MLPAO MLA/T Certification Exam — Questions and Answers

Question 1: In the event of a large chemical spill in the laboratory, the Safety Data Sheet (SDS) is immediately consulted. Which section of the SDS provides the most critical information on how to clean up the spill safely?

Section 7: Handling and Storage
Section 4: First-Aid Measures
Section 6: Accidental Release Measures (Correct answer)
Section 8: Exposure Controls/Personal Protection

Correct answer: Section 6: Accidental Release Measures

Section 6 of a Safety Data Sheet (SDS), titled "Accidental Release Measures," is specifically dedicated to providing procedures for responding to spills, leaks, or releases. This section includes information on containment, cleanup procedures, and necessary precautions to prevent adverse effects on personnel, property, and the environment.

Question 2: Which anticoagulant is used in tubes for the complete blood count (CBC)?

EDTA (ethylenediaminetetraacetic acid) (Correct answer)
Sodium fluoride
Sodium citrate
Lithium heparin

Correct answer: EDTA (ethylenediaminetetraacetic acid)

EDTA (lavender-top tube) is the anticoagulant of choice for CBC testing because it preserves cell morphology and prevents platelet clumping. EDTA chelates calcium ions, preventing coagulation while maintaining cellular integrity for accurate automated and manual cell counting.

Question 3: What is the clinical significance of detecting 'atypical lymphocytes' on a peripheral blood film in a young adult with fever, pharyngitis, and lymphadenopathy?

Suggests acute myeloid leukemia requiring bone marrow biopsy
Suggests infectious mononucleosis caused by Epstein-Barr virus (EBV) (Correct answer)
Is a normal finding in young adults with fever
Suggests bacterial sepsis requiring blood cultures

Correct answer: Suggests infectious mononucleosis caused by Epstein-Barr virus (EBV)

Atypical (reactive) lymphocytes in a young adult with the classic triad of fever, pharyngitis, and lymphadenopathy strongly suggest infectious mononucleosis caused by Epstein-Barr virus (EBV).

Question 4: Which parasitic infection is diagnosed by finding oval eggs with a lateral spine in urine specimens?

Enterobius vermicularis
Trichomonas vaginalis
Schistosoma mansoni
Schistosoma haematobium (Correct answer)

Correct answer: Schistosoma haematobium

Schistosoma haematobium eggs are found in urine and have a characteristic terminal spine. It is the only Schistosoma species that primarily affects the urinary tract, causing hematuria. S. mansoni eggs have a lateral spine and are found in stool. The question describes S. haematobium if the spine is terminal in urine specimens.

Question 5: What is the Rh(D) antigen and why is it clinically significant?

A minor antigen with no clinical relevance
An antigen found only on white blood cells
The most immunogenic red cell antigen after A and B, causing hemolytic disease of the fetus/newborn and transfusion reactions (Correct answer)
An antigen that causes autoimmune disease

Correct answer: The most immunogenic red cell antigen after A and B, causing hemolytic disease of the fetus/newborn and transfusion reactions

The Rh(D) antigen is the most immunogenic non-ABO red cell antigen. D-negative individuals exposed to D-positive red cells (through transfusion or pregnancy) can develop anti-D, which causes hemolytic transfusion reactions and hemolytic disease of the fetus and newborn (HDFN). Rh immunoglobulin (RhIg) prevents alloimmunization.

Question 6: A patient develops urticaria (hives) during a platelet transfusion. There is no fever, hypotension, or respiratory distress. What is the management?

Stop the transfusion permanently
Stop the transfusion, administer antihistamine, and if symptoms resolve, resume the same transfusion at a slower rate (Correct answer)
Give epinephrine immediately
Initiate transfusion reaction investigation for hemolysis

Correct answer: Stop the transfusion, administer antihistamine, and if symptoms resolve, resume the same transfusion at a slower rate

Mild allergic reactions (urticaria only, no systemic symptoms) are managed by temporarily stopping the transfusion, administering an antihistamine (diphenhydramine), and resuming the same unit at a slower rate once symptoms resolve (usually within 30 minutes). If symptoms progress to anaphylaxis (hypotension, bronchospasm), the transfusion must be permanently stopped.

Question 7: Which suffix in medical terminology means 'condition of the blood'?

-itis
-uria
-emia (Correct answer)
-osis

Correct answer: -emia

The suffix '-emia' means 'condition of the blood.' Examples include hyperglycemia (high blood glucose), anemia (low blood hemoglobin), and leukemia (malignant blood cells).

Question 8: A patient has platelet count 15 × 10⁹/L, normal PT/aPTT, and large platelets on the smear. Anti-platelet antibodies are positive. What is the most likely diagnosis?

Thrombotic thrombocytopenic purpura
Immune thrombocytopenia (ITP) (Correct answer)
Aplastic anemia
Disseminated intravascular coagulation

Correct answer: Immune thrombocytopenia (ITP)

The combination of severe isolated thrombocytopenia, normal coagulation studies, large platelets (indicating increased production), and positive anti-platelet antibodies is classic for immune thrombocytopenia (ITP). In ITP, antibodies target platelet surface glycoproteins, leading to accelerated platelet destruction by the spleen.

Question 9: What is the indirect antiglobulin test (IAT) and what does it detect?

It detects antibodies in patient serum/plasma that react with red cell antigens in vitro, using antihuman globulin (AHG) reagent (Correct answer)
It measures red cell antigen strength
It detects complement on patient cells
It detects antibodies bound to red cells in vivo

Correct answer: It detects antibodies in patient serum/plasma that react with red cell antigens in vitro, using antihuman globulin (AHG) reagent

The IAT (indirect Coombs test) detects antibodies in patient serum that have attached to test red cells during incubation. After washing to remove unbound antibodies, antihuman globulin (AHG) reagent is added, which bridges IgG-coated red cells causing visible agglutination. It is used for antibody screening, identification, and crossmatching.

Question 10: What is the normal adult platelet count reference range?

400-600 × 10⁹/L
100-150 × 10⁹/L
50-100 × 10⁹/L
150-400 × 10⁹/L (Correct answer)

Correct answer: 150-400 × 10⁹/L

The normal platelet count range is approximately 150-400 × 10⁹/L. Counts below 150 × 10⁹/L constitute thrombocytopenia, while counts above 400 × 10⁹/L constitute thrombocytosis. Spontaneous bleeding typically does not occur until counts fall below 20-30 × 10⁹/L.

Question 11: A laboratory receives a serum specimen for cortisol measurement labeled 'AM cortisol — 0900 hours.' The specimen was collected at 0900 but not processed until 1600. Is this specimen acceptable?

No, cortisol may degrade; check stability guidelines and consider recollection if outside stability limits (Correct answer)
Yes, cortisol is stable in serum at room temperature for 24 hours
No, cortisol must always be processed within 30 minutes of collection
Yes, if the specimen has not been centrifuged yet

Correct answer: No, cortisol may degrade; check stability guidelines and consider recollection if outside stability limits

Cortisol stability should be verified against laboratory stability data. Most guidelines indicate serum cortisol is stable for 4-8 hours at room temperature and longer if refrigerated, but the 7-hour delay warrants stability verification.

Question 12: What is the reference method for measuring total protein in serum?

Kjeldahl method
Lowry method
Biuret method (Correct answer)
Bradford assay

Correct answer: Biuret method

The biuret method is the standard reference method for measuring total protein in serum. It is based on the reaction of copper ions with peptide bonds in alkaline solution, producing a violet-colored complex measured at 540 nm. It is relatively free from amino acid interference.

Question 13: When collecting a specimen for forensic toxicology testing, what is the most critical procedure that must be meticulously followed to ensure the specimen is admissible in legal proceedings?

Obtaining a fasting sample from the donor.
Using a gray-top tube for collection.
Placing the specimen on ice immediately.
Maintaining a strict chain of custody. (Correct answer)

Correct answer: Maintaining a strict chain of custody.

Chain of custody is the chronological documentation or paper trail, showing the seizure, custody, control, transfer, analysis, and disposition of physical or electronic evidence. For forensic and legal testing, a meticulously maintained chain of custody is essential to prove that the specimen has not been tampered with and to ensure its integrity from collection to reporting.

Question 14: Which of the following is a correct practice when labelling patient specimens in the laboratory?

Electronic labels are not required as long as handwritten labels are present
Specimens must be labelled at the patient's bedside immediately after collection with two patient identifiers (Correct answer)
Labels may be applied before collection to save time if the patient's name is known
Labels can be added later by laboratory staff if the collection team forgets

Correct answer: Specimens must be labelled at the patient's bedside immediately after collection with two patient identifiers

Specimens must be labelled at the point of collection immediately after collection, using at least two patient identifiers (name, date of birth, or health card number), to prevent misidentification.

Question 15: A patient with a mechanical heart valve has an INR target of 2.5-3.5. Their current INR is 2.0. What action should be taken?

Add aspirin instead of adjusting warfarin
No change needed, this is within range
Increase the warfarin dose slightly to achieve the higher target range (Correct answer)
Discontinue warfarin

Correct answer: Increase the warfarin dose slightly to achieve the higher target range

Patients with mechanical heart valves require higher INR targets (typically 2.5-3.5 depending on valve position and type) compared to patients with atrial fibrillation or venous thromboembolism (target 2.0-3.0). An INR of 2.0 is below the therapeutic range and requires a modest dose increase.

Question 16: Which medium is specifically used for isolating Neisseria gonorrhoeae?

Hektoen enteric agar
Thayer-Martin agar (modified) (Correct answer)
MacConkey agar
Sabouraud dextrose agar

Correct answer: Thayer-Martin agar (modified)

Modified Thayer-Martin agar is a chocolate agar-based selective medium containing antibiotics (vancomycin, colistin, nystatin, and trimethoprim) that suppress normal flora while allowing N. gonorrhoeae to grow. The organism requires CO2 enrichment (5-10%) and grows best at 35-37°C.

Question 17: What is the significance of finding eosinophils in a pleural fluid?

Pleural eosinophilia (>10% eosinophils) suggests parasitic infection, drug reaction, malignancy, or prior pneumothorax/hemothorax (Correct answer)
It indicates bacterial pneumonia
Normal finding in all effusions
It has no diagnostic significance

Correct answer: Pleural eosinophilia (>10% eosinophils) suggests parasitic infection, drug reaction, malignancy, or prior pneumothorax/hemothorax

Pleural eosinophilia (>10% eosinophils in pleural fluid) has a specific differential diagnosis including parasitic infection, drug-induced pleuritis, malignancy (especially lymphoma), and prior air or blood in the pleural space. It notably makes tuberculosis very unlikely (<1% of TB effusions have eosinophilia), which can be diagnostically useful.

Question 18: What is autoabsorption and when is it used in the blood bank?

Removing autoantibodies from patient serum using the patient's own red cells to unmask underlying alloantibodies (Correct answer)
Testing patient cells for autoantigens
Adding antibiotics to remove bacterial contamination
Absorbing all antibodies from serum

Correct answer: Removing autoantibodies from patient serum using the patient's own red cells to unmask underlying alloantibodies

Autoabsorption is performed when a patient has warm autoantibodies (warm autoimmune hemolytic anemia) that react with all panel cells, making it impossible to detect underlying alloantibodies. Patient's own red cells (treated with enzymes to enhance adsorption) are incubated with the serum to remove autoantibody, and the absorbed serum is tested for alloantibodies.

Question 19: What are the key differences between thick and thin blood smear examination for malaria diagnosis?

Thick smears are stained differently from thin smears
Thick smears are for species identification; thin smears are for detection
Thick smears concentrate organisms for detection sensitivity; thin smears preserve morphology for species identification (Correct answer)
Both have identical purposes

Correct answer: Thick smears concentrate organisms for detection sensitivity; thin smears preserve morphology for species identification

Thick smears lyse red blood cells and concentrate parasites, providing 10-20 times greater sensitivity for detecting malaria. Thin smears preserve red cell morphology and parasite structure, enabling species identification and parasitemia quantification. Both should be prepared and examined for optimal malaria diagnosis.

Question 20: What is a common cause of falsely elevated potassium in a venous blood specimen?

Elevated plasma protein concentration
Collection in a lithium heparin tube
Delayed centrifugation in a tube without anticoagulant causing cell lysis (Correct answer)
Use of a 21-gauge needle

Correct answer: Delayed centrifugation in a tube without anticoagulant causing cell lysis

Delayed centrifugation of serum tubes allows continued glycolysis by RBCs and release of intracellular potassium (K+) into serum, falsely elevating potassium results — a common pre-analytical error.

Question 21: You are preparing a working solution of NaCl at 0.9% (w/v). How many grams of NaCl are needed to prepare 500 mL of this solution?

45.0 g
9.0 g
4.5 g (Correct answer)
0.9 g

Correct answer: 4.5 g

0.9% w/v means 0.9 g per 100 mL. For 500 mL: 0.9 g × (500/100) = 0.9 × 5 = 4.5 g.

Question 22: What is the purpose of the daily performance verification (DPV) for point-of-care testing (POCT) devices?

To download updated software to the POCT device
To verify the POCT device performs within acceptable limits using quality control materials before patient testing (Correct answer)
To recalibrate the POCT device using primary standards
To verify the test strips have not expired

Correct answer: To verify the POCT device performs within acceptable limits using quality control materials before patient testing

Daily performance verification using QC materials confirms that the POCT device (e.g., glucometer, i-STAT) is functioning correctly before patient results are generated, ensuring result reliability.

Question 23: What are the three components of a complete urinalysis?

Color, clarity, and specific gravity only
Physical examination (colour, clarity, specific gravity), chemical examination (dipstick), and microscopic examination (sediment) (Correct answer)
Dipstick and culture only
Microscopic examination only

Correct answer: Physical examination (colour, clarity, specific gravity), chemical examination (dipstick), and microscopic examination (sediment)

A complete urinalysis includes: 1) Physical examination (colour, clarity/turbidity, specific gravity, odour), 2) Chemical examination (reagent strip/dipstick testing for pH, protein, glucose, ketones, blood, bilirubin, urobilinogen, nitrite, leukocyte esterase, and specific gravity), and 3) Microscopic examination (centrifuged sediment for cells, casts, crystals, and organisms).

Question 24: The laboratory rejects a specimen for INR testing because the specimen is in an evacuated tube with a light blue top and the specimen is:

filled three-quarters full.
spun down for 10 minutes.
delayed in transit for 6 hours. (Correct answer)
separated.
refrigerated for 1 hour before being tested.

Correct answer: delayed in transit for 6 hours.

A specimen for INR testing, collected in a light blue top tube with sodium citrate, is typically rejected if there's a significant delay in transit, such as 6 hours. Coagulation factors are labile and can degrade over time, leading to inaccurate results if not processed or tested within recommended timeframes. Prolonged delays compromise the integrity of the coagulation factors, making the test unreliable.

Question 25: What is the purpose of the modified Kinyoun stain (modified acid-fast stain) in parasitology?

Staining Giardia cysts
Identifying hookworm larvae
Detecting malaria parasites
Detecting Cryptosporidium, Cyclospora, and Isospora oocysts in stool specimens (Correct answer)

Correct answer: Detecting Cryptosporidium, Cyclospora, and Isospora oocysts in stool specimens

The modified acid-fast stain (using a weaker decolorizer than the standard Ziehl-Neelsen) detects partially acid-fast parasites including Cryptosporidium (4-6 µm, round, pink), Cyclospora (8-10 µm, variable staining), and Cystoisospora (Isospora) oocysts in stool. These parasites are not visible on routine ova and parasite examination.

Question 26: Which chromogenic medium is used for screening of MRSA in clinical laboratories?

Blood agar
CHROMagar MRSA or similar chromogenic MRSA medium (Correct answer)
Sabouraud dextrose agar
MacConkey agar

Correct answer: CHROMagar MRSA or similar chromogenic MRSA medium

Chromogenic MRSA media contain cefoxitin (selecting for MRSA) and chromogenic substrates that produce distinctive coloured colonies (typically pink/mauve for S. aureus). These media provide rapid screening results (18-24 hours) for MRSA colonization, which is important for infection prevention and control programs.

Question 27: A 70-year-old patient has WBC 85 × 10⁹/L with 90% mature lymphocytes and numerous smudge cells. What is the most likely diagnosis?

Chronic lymphocytic leukemia (Correct answer)
Infectious mononucleosis
Acute lymphoblastic leukemia
Chronic myeloid leukemia

Correct answer: Chronic lymphocytic leukemia

The clinical picture of an elderly patient with markedly elevated WBC, predominance of mature lymphocytes, and smudge cells (basket cells) is classic for chronic lymphocytic leukemia (CLL). Smudge cells result from the fragility of CLL lymphocytes during smear preparation. Immunophenotyping would show CD5+, CD19+, CD23+ B cells.

Question 28: When is it necessary to collect a trough level for therapeutic drug monitoring (TDM) of vancomycin?

Immediately before the next scheduled vancomycin dose (Correct answer)
30 minutes after the start of the vancomycin infusion
2 hours after the infusion is complete
At any time, as vancomycin levels are constant throughout the dosing interval

Correct answer: Immediately before the next scheduled vancomycin dose

Vancomycin trough levels are collected immediately before the next scheduled dose (at the lowest point in the dosing interval) to assess drug accumulation, dosing adequacy, and risk of toxicity.

Question 29: What is the primary clinical use of measuring glycated hemoglobin (HbA1c)?

Detecting insulin resistance
Monitoring long-term glycemic control (Correct answer)
Screening for gestational diabetes
Diagnosing acute hypoglycemia

Correct answer: Monitoring long-term glycemic control

HbA1c reflects average blood glucose levels over the preceding 2-3 months, corresponding to the lifespan of red blood cells. It is used to monitor long-term glycemic control in diabetic patients and is also accepted as a diagnostic criterion for diabetes mellitus.

Question 30: What is the shelf life of refrigerated red blood cells stored in CPDA-1 anticoagulant?

7 days
21 days
35 days (Correct answer)
42 days

Correct answer: 35 days

Red blood cells stored in CPDA-1 have a shelf life of 35 days at 1-6°C. With additive solutions (AS-1, AS-3, AS-5), the shelf life extends to 42 days. Proper storage temperature must be maintained and monitored continuously. Outdated units must be discarded to ensure adequate post-transfusion red cell recovery (>75% at 24 hours).

Question 31: Which coagulation test measures the extrinsic and common pathways?

Prothrombin time (PT) (Correct answer)
Fibrinogen assay
Thrombin time (TT)
Activated partial thromboplastin time (aPTT)

Correct answer: Prothrombin time (PT)

The prothrombin time (PT) measures the extrinsic (Factor VII) and common (Factors X, V, II, and fibrinogen) coagulation pathways. It is triggered by adding tissue thromboplastin (tissue factor) and calcium to citrated plasma. PT/INR is used to monitor warfarin therapy.

Question 32: What is the CAMP test used to identify?

Listeria monocytogenes
Group B Streptococcus (Streptococcus agalactiae) (Correct answer)
Staphylococcus aureus
Enterococcus faecalis

Correct answer: Group B Streptococcus (Streptococcus agalactiae)

The CAMP test identifies Group B Streptococcus (S. agalactiae) by demonstrating enhanced hemolysis in the shape of an arrowhead where the CAMP factor of GBS intersects with the beta-hemolysin of Staphylococcus aureus on a blood agar plate. GBS is a critical pathogen in neonatal sepsis and meningitis.

Question 33: The cellular morphology of a cytological preparation is distorted when smears are:

left in the clearing solution for a 1/2 hour.
left in the fixative solution for longer than 2 hours.
left in the stain solution for a 1/2 hour.
allowed to dry prior to staining. (Correct answer)
allowed to dry prior to coverslipping.

Correct answer: allowed to dry prior to staining.

In cytological preparations, allowing smears to air dry prior to fixation and staining causes significant cellular distortion, known as 'air-drying artifact.' This artifact leads to cell shrinkage, nuclear pyknosis, and altered cytoplasmic features, making accurate morphological interpretation difficult or impossible. Prompt fixation, typically with alcohol, is crucial to preserve cellular detail and prevent these artifacts.

Question 34: A 2-year-old patient requires blood collection. Which specimen collection method is most appropriate?

Standard venipuncture from the antecubital fossa using a 21-gauge needle
Arterial puncture from the radial artery
Capillary puncture from the heel or fingertip using a lancet (Correct answer)
Central venous catheter access only

Correct answer: Capillary puncture from the heel or fingertip using a lancet

Capillary puncture is the preferred method for young children as it is less invasive, requires smaller volumes, and is appropriate for the types of tests typically ordered in pediatric patients.

Question 35: A technologist notices that the automated WBC count is 25 × 10⁹/L but the histogram shows a suspicious population. The peripheral smear shows many nucleated red blood cells (NRBCs). What should be reported?

Only the NRBC count
A corrected WBC count after subtracting NRBCs from the total count (Correct answer)
The automated count with a comment that NRBCs are present but no correction
The automated WBC count without correction

Correct answer: A corrected WBC count after subtracting NRBCs from the total count

NRBCs have nuclei and are counted as WBCs by automated analyzers that use lysis-resistant nuclear counting. The WBC count must be corrected using the formula: Corrected WBC = (Automated WBC × 100) / (100 + NRBC per 100 WBC). The presence of NRBCs and the corrected count should both be reported.

Question 36: Which risk is NOT associated with the following WHMIS symbol?

May react with water
May explode if exposed to shock or heat
May cause environmental damage from fumes (Correct answer)
May burn unexpectedly
May be chemically unstable

Correct answer: May cause environmental damage from fumes

This risk is not typically associated with the WHMIS symbol for explosive materials. Explosive hazards are more about the potential for sudden reactions, instability, burning, or explosions due to shock, heat, or contact with water. Environmental damage from fumes would be associated with a different hazard symbol, such as one for environmental hazards or toxic substances.

Question 37: A laboratory quality indicator shows the turnaround time (TAT) for STAT potassium results has increased from 45 minutes to 90 minutes over the past month. Which quality management tool would best identify the root cause?

Fishbone (Ishikawa) diagram (Correct answer)
Histogram of daily QC results
Standard deviation calculation
Levey-Jennings chart

Correct answer: Fishbone (Ishikawa) diagram

A fishbone (Ishikawa) diagram is a cause-and-effect tool used to systematically identify potential root causes of a quality problem across categories such as people, methods, equipment, and materials.

Question 38: A laboratory receives a hemolyzed specimen for potassium analysis. The measured potassium is 6.8 mmol/L. What is the most appropriate course of action?

Report the result with a delta check notation
Dilute the specimen 1:2 and multiply the result by 2
Reject the specimen, document hemolysis, and request a recollection (Correct answer)
Accept the result as potassium is stable in hemolyzed samples

Correct answer: Reject the specimen, document hemolysis, and request a recollection

Hemolysis releases intracellular potassium (up to 30× higher than plasma), causing falsely elevated results. The specimen must be rejected and recollected.

Question 39: What is the role of Canadian Blood Services (CBS) in the Canadian blood system?

CBS is responsible for collecting, testing, processing, and distributing blood and blood products across Canada (except Québec, which is served by Héma-Québec) (Correct answer)
CBS only tests blood for infectious diseases
CBS provides blood products only in Ontario
CBS is a private for-profit company

Correct answer: CBS is responsible for collecting, testing, processing, and distributing blood and blood products across Canada (except Québec, which is served by Héma-Québec)

Canadian Blood Services (CBS) is the national, not-for-profit blood operator responsible for the collection, testing, processing, and distribution of blood and blood products for all Canadian provinces and territories except Québec (served by Héma-Québec). CBS also manages the national stem cell, organ, and tissue donation programs.

Question 40: According to CMLTO standards, which class of fire extinguisher is appropriate for electrical equipment fires in a medical laboratory?

Class D
Class A
Class B
Class C (Correct answer)

Correct answer: Class C

Class C extinguishers are designed for electrical fires and use non-conductive agents, making them safe for use on energized electrical equipment found in laboratories.

Question 41: Which analyte requires collection in a tube containing sodium fluoride to prevent glycolysis?

Calcium
Bilirubin
Glucose (Correct answer)
Potassium

Correct answer: Glucose

Glucose specimens require sodium fluoride (grey-top tube) to inhibit glycolysis by red blood cells and white blood cells. Without this preservative, glucose decreases approximately 5-7% per hour at room temperature due to continued cellular metabolism.

Question 42: When collecting a blood specimen using a winged infusion set (butterfly) and an evacuated tube system for a single coagulation test (light blue top), what is the correct procedure?

Collect the light blue top tube first without any special preparation.
Vigorously shake the tube after collection to mix the anticoagulant.
Draw a discard tube before the light blue top tube. (Correct answer)
Underfill the light blue top tube to compensate for the air in the tubing.

Correct answer: Draw a discard tube before the light blue top tube.

The tubing of a winged infusion set contains air. If the light blue (sodium citrate) tube is the first or only tube drawn, this air will enter the tube first, preventing it from filling to the proper volume. This would alter the critical 9:1 blood-to-anticoagulant ratio, invalidating coagulation test results. A discard tube (a plain red top or another light blue top) must be drawn first to purge the air from the tubing.

Question 43: During aerobic respiration, what molecule is the final electron acceptor in the electron transport chain?

Oxygen (Correct answer)
Carbon dioxide
Glucose
NAD+

Correct answer: Oxygen

Oxygen is the final electron acceptor in the electron transport chain, combining with electrons and protons to form water (H₂O) at Complex IV (cytochrome c oxidase).

Question 44: What is Beer's Law and how does it apply to clinical chemistry?

It describes the relationship between temperature and reaction rate
It defines the relationship between pH and pKa
It states that absorbance is directly proportional to the concentration of the absorbing substance and path length (Correct answer)
It describes the equilibrium between bound and free drug

Correct answer: It states that absorbance is directly proportional to the concentration of the absorbing substance and path length

Beer's Law (A = εbc) states that absorbance is directly proportional to the molar absorptivity (ε), path length (b), and concentration (c) of the absorbing substance. This is the fundamental principle underlying spectrophotometric measurements in clinical chemistry, allowing concentration to be determined from absorbance readings.

Question 45: What is the significance of measuring C-reactive protein (CRP) in clinical chemistry?

Evaluating thyroid function
Measuring complement activation
Assessing nutritional status
Detecting and monitoring inflammation and infection (Correct answer)

Correct answer: Detecting and monitoring inflammation and infection

CRP is an acute phase protein produced by the liver in response to inflammation. It rises rapidly (within 6-8 hours) and can increase up to 1000-fold during acute infection or inflammation. High-sensitivity CRP (hs-CRP) is also used for cardiovascular risk assessment.

Question 46: Which of the following is the most appropriate site for capillary blood collection in a premature neonate?

Medial or lateral plantar surface of the heel (Correct answer)
Big toe
Earlobe
Fingertip of the third or fourth finger

Correct answer: Medial or lateral plantar surface of the heel

The medial or lateral plantar surface of the heel is the approved capillary collection site for neonates and premature infants. Fingertips must never be used in neonates due to risk of bone injury.

Question 47: Which culture medium is selective and differential for the isolation of Salmonella and Shigella from stool specimens?

Blood agar
Chocolate agar
Salmonella-Shigella (SS) agar or Hektoen enteric agar (Correct answer)
MacConkey agar

Correct answer: Salmonella-Shigella (SS) agar or Hektoen enteric agar

SS agar and Hektoen enteric agar are selective (inhibiting normal flora with bile salts and dyes) and differential (detecting lactose fermentation and H2S production) media designed to isolate enteric pathogens.

Question 48: A patient has pancytopenia with 25% blasts in the peripheral blood. What is the most likely category of disease?

Acute leukemia (Correct answer)
Chronic myeloproliferative neoplasm
Vitamin B12 deficiency
Aplastic anemia

Correct answer: Acute leukemia

The presence of ≥20% blasts in peripheral blood or bone marrow defines acute leukemia (by WHO classification). Pancytopenia results from marrow replacement by leukemic blasts, suppressing normal hematopoiesis. Flow cytometry and cytogenetics are needed to classify as AML or ALL and determine prognosis.

Question 49: Which specimen processing step is critical for recovery of Mycobacterium tuberculosis from sputum?

Direct inoculation onto blood agar
Digestion and decontamination with NALC-NaOH (Correct answer)
Enrichment in thioglycollate broth
Filtration through a 0.22 µm membrane

Correct answer: Digestion and decontamination with NALC-NaOH

Sputum specimens for mycobacterial culture require digestion and decontamination with N-acetyl-L-cysteine (NALC) as a mucolytic agent and sodium hydroxide (NaOH) to kill contaminating bacteria. This step is critical because mycobacteria grow slowly (2-8 weeks) and would be overgrown by faster-growing normal flora.

Question 50: A CSF specimen has elevated protein, low glucose, elevated WBC with neutrophil predominance, and the Gram stain shows gram-negative diplococci. What is the most likely pathogen?

Haemophilus influenzae
Streptococcus pneumoniae
Listeria monocytogenes
Neisseria meningitidis (Correct answer)

Correct answer: Neisseria meningitidis

Gram-negative diplococci (kidney-bean shaped) in CSF with a bacterial meningitis profile (high protein, low glucose, neutrophilic pleocytosis) is classic for Neisseria meningitidis. This is a medical emergency requiring immediate ceftriaxone therapy and close contact prophylaxis with rifampin or ciprofloxacin. It is reportable to public health.

Question 51: A laboratory receives a synovial fluid specimen from a joint aspiration. Which finding on microscopic examination would confirm the diagnosis of gout?

Negatively birefringent needle-shaped crystals (monosodium urate) under polarized light microscopy (Correct answer)
Positively birefringent rhomboid crystals (calcium pyrophosphate)
Abundant neutrophils without crystals
Gram-positive cocci in clusters

Correct answer: Negatively birefringent needle-shaped crystals (monosodium urate) under polarized light microscopy

Gout is confirmed by the presence of negatively birefringent needle-shaped monosodium urate (MSU) crystals within or outside white blood cells under compensated polarized light microscopy.

Question 52: What is the proper technique for body fluid cytocentrifugation?

Air-dry the fluid on a slide
Concentrate cells by centrifuging fluid in a specialized chamber that deposits a monolayer of cells onto a glass slide for staining and morphological examination (Correct answer)
Filter the fluid through paper
Smear the fluid directly on a slide

Correct answer: Concentrate cells by centrifuging fluid in a specialized chamber that deposits a monolayer of cells onto a glass slide for staining and morphological examination

Cytocentrifugation (using a Cytospin centrifuge) concentrates cells from body fluids onto a defined area of a glass slide, creating a monolayer suitable for Wright-Giemsa staining and differential counting. This technique preserves cell morphology better than regular centrifugation and is essential for accurate differential counts on low-cellularity fluids.

Question 53: What is the principle of blood culture gram stain and how should results be communicated?

Results are communicated within 24 hours as routine
Gram stain is only performed after subculture growth
Results are only communicated if the organism is identified to species
Gram stain is performed immediately when the instrument flags positive, and results are communicated urgently to the physician (Correct answer)

Correct answer: Gram stain is performed immediately when the instrument flags positive, and results are communicated urgently to the physician

When an automated blood culture system flags a bottle as positive, the Gram stain is performed immediately to provide preliminary organism identification. This result must be communicated urgently (STAT) to the physician as it guides empiric antibiotic therapy. The Gram stain morphology (e.g., gram-positive cocci in clusters) is critical for initial treatment decisions.

Question 54: A physician in the ER performs a lumbar puncture on a patient. Which of the following tests are likely to be ordered?

INR, Urea, lytes, creatinine
CBC, PT, PTT
Group and screen and crossmatch
Glucose, protein, Gram's stain, cell count (Correct answer)
AST, ALT, Alk. Phos

Correct answer: Glucose, protein, Gram's stain, cell count

When a physician performs a lumbar puncture to collect cerebrospinal fluid (CSF), the primary tests ordered are typically for diagnosing infections, inflammation, or other neurological conditions. Therefore, a cell count (to check for increased white blood cells), glucose and protein levels (to assess for infection or inflammation), and a Gram's stain (to identify bacterial pathogens) are standard and crucial analyses performed on CSF.

Question 55: Which enzyme is measured to confirm the hepatic origin of an elevated alkaline phosphatase?

Creatine kinase (CK)
Alanine aminotransferase (ALT)
Amylase
Gamma-glutamyltransferase (GGT) (Correct answer)

Correct answer: Gamma-glutamyltransferase (GGT)

GGT is used to confirm the hepatic origin of an elevated alkaline phosphatase. If both ALP and GGT are elevated, the ALP is likely of hepatobiliary origin. If ALP is elevated but GGT is normal, the ALP elevation is likely from bone or other non-hepatic sources.

Question 56: What is the Lewis blood group system and why are Lewis antibodies usually clinically insignificant?

Lewis antigens are found only on white blood cells
Lewis antibodies are always clinically significant
Lewis antibodies are IgG and cross the placenta
Lewis antibodies are typically IgM, cold-reactive, and do not cause HDFN because Lewis antigens are not well-developed on fetal red cells and are adsorbed from plasma (Correct answer)

Correct answer: Lewis antibodies are typically IgM, cold-reactive, and do not cause HDFN because Lewis antigens are not well-developed on fetal red cells and are adsorbed from plasma

Lewis antibodies (anti-Lea, anti-Leb) are typically IgM, react at room temperature or below, and are usually clinically insignificant. Lewis antigens are not intrinsic to the red cell membrane but are adsorbed from plasma, so they are not well-developed on fetal red cells (no HDFN risk). Lewis antibodies may be neutralized by Lewis substance in transfused plasma.

Question 57: When storing serum specimens for up to 7 days pending batch analysis, what is the appropriate storage temperature?

Refrigerator (2-8°C) (Correct answer)
Room temperature (15-25°C)
Ultra-low freezer (-70°C) for all analytes
Freezer (-20°C)

Correct answer: Refrigerator (2-8°C)

For short-term storage (up to 7 days), most serum chemistry analytes are stable when refrigerated at 2-8°C. This temperature slows enzymatic degradation and bacterial growth without causing freeze-thaw damage.

Question 58: What is the difference between the direct antiglobulin test (DAT) and the indirect antiglobulin test (IAT)?

They test for the same thing
DAT uses patient serum; IAT uses patient cells
DAT detects antibodies already bound to patient red cells in vivo; IAT detects antibodies in patient serum that bind to test red cells in vitro (Correct answer)
DAT is more sensitive than IAT

Correct answer: DAT detects antibodies already bound to patient red cells in vivo; IAT detects antibodies in patient serum that bind to test red cells in vitro

The DAT (direct Coombs test) detects IgG or complement already bound to the patient's red cells in the circulation (in vivo sensitization). The IAT (indirect Coombs test) detects free antibodies in patient serum that bind to test red cells during laboratory incubation (in vitro sensitization). The DAT is used for transfusion reaction investigation and autoimmune hemolytic anemia.

Question 59: What type of quality control chart is used to monitor the mean and variation of laboratory analytical results over time?

Scatter plot
Pareto chart
Levey-Jennings chart (Correct answer)
Run chart only

Correct answer: Levey-Jennings chart

The Levey-Jennings chart plots QC results over time against mean and ±1, ±2, and ±3 SD control limits, allowing visual detection of shifts, trends, and random error in laboratory analytical performance.

Question 60: Which method is most commonly used for measuring serum glucose in clinical chemistry analyzers?

Ortho-toluidine method
Folin-Wu method
Somogyi-Nelson method
Hexokinase method (Correct answer)

Correct answer: Hexokinase method

The hexokinase method is the reference method for glucose measurement. It uses hexokinase to phosphorylate glucose to glucose-6-phosphate, which is then oxidized by glucose-6-phosphate dehydrogenase with production of NADPH, measured spectrophotometrically.

Question 61: What is the preferred urine specimen for routine urinalysis?

First morning midstream clean-catch specimen (Correct answer)
Post-prandial specimen
24-hour collection
Random collection

Correct answer: First morning midstream clean-catch specimen

The first morning midstream clean-catch specimen is preferred for routine urinalysis because it is the most concentrated, maximizing the detection of chemical constituents and formed elements. Midstream collection reduces contamination from urethral flora and epithelial cells. Proper patient instruction is essential for specimen quality.

Question 62: In flow cytometry, CD4:CD8 ratio is used clinically to monitor patients with HIV. A significantly decreased ratio (below 1.0) indicates:

A normal healthy immune response
Polyclonal B cell activation
Progressive immunodeficiency due to CD4+ T cell depletion (Correct answer)
Increased natural killer cell activity

Correct answer: Progressive immunodeficiency due to CD4+ T cell depletion

HIV selectively destroys CD4+ T helper cells, causing the CD4:CD8 ratio to fall below normal (normal ~2:1); a ratio below 1.0 indicates significant immune compromise and disease progression.

Question 63: What is the India ink preparation used to detect?

Plasmodium species
Cryptococcus neoformans capsule in CSF (Correct answer)
Acid-fast bacilli
Gram-negative diplococci

Correct answer: Cryptococcus neoformans capsule in CSF

The India ink preparation is a negative staining technique that reveals the thick polysaccharide capsule of Cryptococcus neoformans in CSF. The ink particles are excluded by the capsule, creating a clear halo around the yeast cell against a dark background. The cryptococcal antigen test (CrAg) has largely replaced India ink due to higher sensitivity.

Question 64: Which organelle is responsible for ATP production through oxidative phosphorylation in human cells?

Golgi apparatus
Nucleus
Mitochondria (Correct answer)
Ribosome

Correct answer: Mitochondria

Mitochondria are the sites of oxidative phosphorylation, producing the majority of cellular ATP through the electron transport chain and the citric acid cycle.

Question 65: Which staining method is used to identify Pneumocystis jirovecii in respiratory specimens?

Acid-fast stain
Gram stain
Wright-Giemsa stain only
Gomori methenamine silver (GMS) stain or immunofluorescence (Correct answer)

Correct answer: Gomori methenamine silver (GMS) stain or immunofluorescence

Gomori methenamine silver (GMS) stain highlights the cyst wall of Pneumocystis jirovecii as dark brown/black against a green background. Direct fluorescent antibody (DFA) testing is more sensitive and specific. PCR is increasingly used as it can detect both cystic and trophic forms. P. jirovecii causes pneumonia in immunocompromised patients.

Question 66: The routine performance verification for a laboratory centrifuge must include checking which two critical parameters to ensure proper specimen separation and quality?

Rotational speed (RPM) and timer accuracy (Correct answer)
Lid gasket integrity and internal temperature
Rotor balance and vibration frequency
Electrical safety and noise level

Correct answer: Rotational speed (RPM) and timer accuracy

According to CLSI guidelines and best practices, the two most critical performance parameters to verify on a centrifuge are the rotational speed (tachometer reading) and the timer's accuracy. These ensure that the correct relative centrifugal force (RCF) is applied for the specified duration, which is essential for adequate specimen separation.

Question 67: Which specimen collection error would falsely decrease measured serum calcium?

Collecting in an EDTA tube instead of a red-top tube (Correct answer)
Using a serum separator tube
Hemolysis of the specimen
Prolonged tourniquet application

Correct answer: Collecting in an EDTA tube instead of a red-top tube

Collecting blood in an EDTA tube (lavender top) for calcium measurement would give falsely decreased results because EDTA chelates (binds) calcium ions. EDTA is an anticoagulant that works specifically by removing calcium, which is essential for the coagulation cascade.

Question 68: Which vein is considered the preferred primary site for adult venipuncture and why?

Basilic vein — it is the largest and most accessible
Dorsal hand veins — they are the safest and most accessible
Median cubital vein — it is large, well-anchored, and has few nearby nerves and arteries (Correct answer)
Cephalic vein — it is most visible in all patients

Correct answer: Median cubital vein — it is large, well-anchored, and has few nearby nerves and arteries

The median cubital vein is the preferred first-choice venipuncture site because it is typically large, well-supported by subcutaneous tissue, well-anchored, and relatively distant from major arteries and nerves.

Question 69: What is the maximum time a peripheral blood smear should be made after collecting an EDTA blood sample for accurate WBC differential?

Within 4 hours if refrigerated
Within 24 hours if stored at room temperature
Within 1 hour of collection
Within 30 minutes of collection (Correct answer)

Correct answer: Within 30 minutes of collection

Blood smears for WBC differential should ideally be made within 30 minutes of collection to prevent cellular morphology changes, particularly neutrophil lobulation and lymphocyte vacuolation.

Question 70: Which specimen type is preferred for most clinical chemistry analyses?

Plasma from a heparin tube
Capillary blood
Whole blood in EDTA
Serum from a red-top tube (Correct answer)

Correct answer: Serum from a red-top tube

Serum collected in a red-top (no additive) tube or serum separator tube (SST) is preferred for most clinical chemistry analyses. Serum lacks fibrinogen and clotting factors, providing a cleaner matrix that minimizes interference with many analytical methods.

Question 71: What is the Henderson-Hasselbalch equation used to calculate in clinical chemistry?

Creatinine clearance
Blood pH from bicarbonate and pCO2 (Correct answer)
Osmolal gap
Anion gap

Correct answer: Blood pH from bicarbonate and pCO2

The Henderson-Hasselbalch equation calculates blood pH from the ratio of bicarbonate concentration to dissolved CO2 (pCO2). The equation is pH = pK + log([HCO3-]/[0.03 × pCO2]), and it is fundamental to understanding acid-base physiology.

Question 72: What is the principle of the ion-selective electrode used for measuring ionized calcium?

Amperometry using a platinum electrode
Potentiometry using a calcium-selective membrane (Correct answer)
Conductimetry measuring total ionic strength
Coulometry using an electrolytic cell

Correct answer: Potentiometry using a calcium-selective membrane

Ionized calcium is measured by potentiometry using an electrode with a calcium-selective membrane (typically containing a calcium-selective ionophore). The electrode generates a voltage proportional to the logarithm of ionized calcium activity in the specimen.

Question 73: A patient has prolonged PT and aPTT that both correct on mixing with normal plasma. Which condition is most likely?

Multiple factor deficiency (such as liver disease or DIC) (Correct answer)
Factor VIII inhibitor
Antiphospholipid syndrome
Lupus anticoagulant

Correct answer: Multiple factor deficiency (such as liver disease or DIC)

When both PT and aPTT are prolonged and correct on mixing, it indicates deficiency of one or more coagulation factors in both pathways. Common causes include liver disease (decreased synthesis), DIC (consumption), and vitamin K deficiency. Inhibitors would not correct on mixing study.

Question 74: Which preanalytical factor causes pseudohyperkalemia?

Fist clenching during venipuncture (Correct answer)
Patient dehydration
Use of a serum separator tube
Short tourniquet application

Correct answer: Fist clenching during venipuncture

Repeated fist clenching during venipuncture causes potassium release from forearm muscle cells, leading to pseudohyperkalemia. Patients should be instructed to keep their fist still during blood collection. Other causes include hemolysis and extreme leukocytosis or thrombocytosis.

Question 75: Which blood type is considered the universal recipient for red blood cell transfusions?

Type B negative
Type A positive
Type O negative
Type AB positive (Correct answer)

Correct answer: Type AB positive

Type AB positive individuals are universal recipients for red blood cells because they have no ABO antibodies and have the Rh(D) antigen, so they can receive RBCs of any ABO and Rh(D) type.

Question 76: What is the principle of the quantitative immunoglobulin measurement by nephelometry?

Measurement of enzyme activity after antibody-antigen complex formation
Detection of immunoglobulin gene rearrangements by PCR
Measurement of light scattered by antigen-antibody complexes to determine protein concentration (Correct answer)
Separation of immunoglobulins by molecular weight before quantification

Correct answer: Measurement of light scattered by antigen-antibody complexes to determine protein concentration

Nephelometry measures the intensity of laser light scattered at an angle by antigen-antibody complexes formed when patient immunoglobulins bind to specific antibody reagents. Scatter intensity is proportional to protein concentration.

Question 77: A patient has PT 18 seconds (normal 11-14), aPTT 45 seconds (normal 25-35), low fibrinogen, elevated D-dimer, and schistocytes on smear. What is the most likely diagnosis?

Primary fibrinolysis
Vitamin K deficiency
Liver cirrhosis
Disseminated intravascular coagulation (Correct answer)

Correct answer: Disseminated intravascular coagulation

The combination of prolonged PT and aPTT, low fibrinogen, elevated D-dimer, and schistocytes is the classic laboratory picture of DIC. This consumptive coagulopathy results in simultaneous coagulation factor consumption, fibrinolysis activation, and microangiopathic hemolysis. The underlying cause must be identified and treated.

Question 78: What is the role of erythropoietin (EPO) in hematopoiesis?

Stimulates platelet production
Stimulates red blood cell production in response to hypoxia (Correct answer)
Stimulates white blood cell production
Inhibits bone marrow stem cell differentiation

Correct answer: Stimulates red blood cell production in response to hypoxia

Erythropoietin is a glycoprotein hormone produced primarily by the kidneys in response to tissue hypoxia. It stimulates erythroid progenitor cells in the bone marrow to proliferate and differentiate into mature red blood cells. Chronic kidney disease reduces EPO production, causing anemia.

Question 79: A patient types as group A on forward typing but group O on reverse typing. What should the technologist investigate?

Report as group A
Report as group O
Investigate the ABO discrepancy — possible weak A subgroup, missing anti-B, cold antibodies, or technical error (Correct answer)
Repeat forward typing only

Correct answer: Investigate the ABO discrepancy — possible weak A subgroup, missing anti-B, cold antibodies, or technical error

An ABO discrepancy (forward and reverse do not agree) must be investigated before a blood type is assigned. This pattern (A forward, O reverse) could indicate a weak A subgroup (A2, Ax) where the patient has anti-A1 as well as expected anti-B. Additional testing includes anti-A1 lectin, A1 and A2 cells, room temperature incubation, and patient history review.

Question 80: Which molecular test is used for rapid detection of Mycobacterium tuberculosis and rifampin resistance?

GeneXpert MTB/RIF (Xpert) (Correct answer)
Interferon-gamma release assay
Mantoux tuberculin skin test
AFB culture on Lowenstein-Jensen medium

Correct answer: GeneXpert MTB/RIF (Xpert)

GeneXpert MTB/RIF is a rapid, cartridge-based NAAT that simultaneously detects M. tuberculosis complex and rifampin resistance within 2 hours directly from clinical specimens. It targets the rpoB gene and has revolutionized TB diagnosis globally. It is particularly valuable in Canadian settings for rapid diagnosis and public health response.

Question 81: Which type of error is characterized by results that are consistently higher or lower than the true value?

Systematic error (bias) (Correct answer)
Gross error
Preanalytical error
Random error

Correct answer: Systematic error (bias)

Systematic error (bias) produces results that are consistently displaced in one direction from the true value. It can be constant (same magnitude regardless of concentration) or proportional (error changes with concentration). Causes include calibration errors, reagent deterioration, and matrix effects.

Question 82: What is the function of a micropipette calibration check using gravimetric analysis?

To check the pipette tip for contamination
To verify the pipette delivers the correct volume by weighing dispensed water (Correct answer)
To verify the electrical calibration of the analyzer
To measure the viscosity of reagents

Correct answer: To verify the pipette delivers the correct volume by weighing dispensed water

Gravimetric calibration checks a micropipette's accuracy by weighing aliquots of distilled water dispensed at the set volume, using the known density of water (1.00 g/mL at 20°C) to calculate the delivered volume.

Question 83: Which phase of mitosis involves the separation of sister chromatids to opposite poles of the cell?

Metaphase
Telophase
Prophase
Anaphase (Correct answer)

Correct answer: Anaphase

Anaphase is the phase of mitosis when sister chromatids separate and move to opposite poles of the cell, pulled by spindle fibers attached to centromeres.

Question 84: What does the urine specific gravity measure?

The number of cells in urine
Urine pH
The concentration of dissolved solutes in urine relative to water (Correct answer)
Urine volume

Correct answer: The concentration of dissolved solutes in urine relative to water

Specific gravity measures the density of urine compared to pure water (1.000), reflecting the kidney's ability to concentrate or dilute urine. Normal range is 1.005-1.030. High specific gravity (>1.030) indicates concentrated urine (dehydration), while low specific gravity (1.001-1.005) indicates dilute urine. Fixed specific gravity (1.010) suggests renal tubular dysfunction.

Question 85: What does proteinuria detected by dipstick primarily measure?

Only Bence Jones protein
All proteins equally
Primarily albumin (the indicator is more sensitive to albumin than other proteins) (Correct answer)
Only hemoglobin

Correct answer: Primarily albumin (the indicator is more sensitive to albumin than other proteins)

The urine dipstick protein pad uses a pH indicator (tetrabromophenol blue) that is primarily sensitive to albumin due to the protein error of indicators principle. It may miss low-molecular-weight proteins like Bence Jones protein (immunoglobulin light chains). Sulfosalicylic acid (SSA) or total protein measurement detects all proteins.

Question 86: What is the mucin clot test (Ropes test) used for in synovial fluid analysis?

Testing for bacterial infection
Assessing the quality of hyaluronic acid in synovial fluid; a poor clot suggests inflammatory degradation of hyaluronic acid (Correct answer)
Detecting crystals
Measuring glucose levels

Correct answer: Assessing the quality of hyaluronic acid in synovial fluid; a poor clot suggests inflammatory degradation of hyaluronic acid

The mucin clot test assesses hyaluronic acid integrity by adding acetic acid to synovial fluid. Normal synovial fluid forms a firm, cohesive clot (good mucin clot). Inflammatory conditions (rheumatoid arthritis, septic arthritis) degrade hyaluronic acid through enzymatic action, producing a poor or friable clot. This test has largely been replaced by more specific analyses.

Question 87: A laboratory is setting up a highly sensitive trace element analysis. According to CLSI standards, what is the minimum grade of reagent water that should be used for preparing calibrators and standards for this procedure?

Special Reagent Water (SRW)
Type III
Type II
Clinical Laboratory Reagent Water (CLRW) (Correct answer)

Correct answer: Clinical Laboratory Reagent Water (CLRW)

Clinical Laboratory Reagent Water (CLRW) is the minimum standard for most routine clinical analyses. It has defined limits for resistivity, bacteria, and total organic carbon. While some highly specialized tests may require Special Reagent Water (SRW) with even stricter limits for specific contaminants, CLRW is the established baseline for preparing most reagents, calibrators, and controls.

Question 88: A urine microscopy report shows 15–20 RBCs per high-power field (HPF). This finding is best described as:

Normal finding
Pseudohematuria
Gross hematuria
Microscopic hematuria (Correct answer)

Correct answer: Microscopic hematuria

More than 3–5 RBCs/HPF is defined as microscopic hematuria. 15–20 RBCs/HPF is a clearly abnormal finding requiring clinical follow-up.

Question 89: A patient has WBC 150 × 10⁹/L with a differential showing a full spectrum of myeloid maturation from blasts to mature neutrophils, basophilia, and splenomegaly. What is the most likely diagnosis?

Myelofibrosis
Leukemoid reaction
Acute myeloid leukemia
Chronic myeloid leukemia (Correct answer)

Correct answer: Chronic myeloid leukemia

The hallmark of CML is an extremely elevated WBC with a complete spectrum of myeloid maturation ('pathological left shift'), basophilia, and massive splenomegaly. Unlike AML (blast predominance) or leukemoid reaction (no basophilia, positive LAP score), CML shows orderly maturation. Philadelphia chromosome/BCR-ABL1 testing confirms the diagnosis.

Question 90: What does an elevated reticulocyte count indicate?

Iron deficiency
Chronic disease
Bone marrow failure
Increased red blood cell production (erythropoietic response) (Correct answer)

Correct answer: Increased red blood cell production (erythropoietic response)

An elevated reticulocyte count indicates increased erythropoietic activity in the bone marrow, typically in response to anemia, blood loss, or hemolysis. Reticulocytes are immature red blood cells that still contain residual RNA and mature in the circulation within 1-2 days.

Question 91: What is the appropriate response when a laboratory receives a telephone request to release patient results to someone claiming to be the patient's physician?

Release results immediately to maintain good clinical service
Refuse all telephone result requests as a matter of policy
Verify the caller's identity using established laboratory protocols before releasing information (Correct answer)
Request the caller's cell phone number for follow-up verification

Correct answer: Verify the caller's identity using established laboratory protocols before releasing information

Before releasing patient health information by telephone, the laboratory must verify the caller's identity using established protocols such as call-back procedures or registered access codes.

Question 92: Rheumatoid factor (RF) is typically an autoantibody of which immunoglobulin class directed against:

IgG directed against nuclear antigens
IgM directed against patient's own IgG (Correct answer)
IgE directed against IgM
IgA directed against collagen

Correct answer: IgM directed against patient's own IgG

Rheumatoid factor is classically an IgM autoantibody that targets the Fc region of the patient's own IgG, forming immune complexes that contribute to inflammation in rheumatoid arthritis.

Question 93: What is the principle behind the enzymatic method for measuring serum triglycerides?

Direct spectrophotometric absorption of triglycerides
Thin-layer chromatography separation
Lipase hydrolysis followed by glycerol kinase reaction (Correct answer)
Saponification with potassium hydroxide

Correct answer: Lipase hydrolysis followed by glycerol kinase reaction

The enzymatic method for triglycerides involves lipase hydrolysis to release glycerol, which is then phosphorylated by glycerol kinase. Subsequent enzymatic reactions produce a colored compound or hydrogen peroxide that is measured spectrophotometrically.

Question 94: Which of the following is considered the most effective method for verifying that a steam autoclave cycle has successfully achieved sterilization?

Using heat-sensitive autoclave tape on the exterior of the packages
Observing that the pressure and temperature gauges reached the required settings
Placing a chemical indicator strip in the center of the load
Processing a biological indicator containing Geobacillus stearothermophilus spores (Correct answer)

Correct answer: Processing a biological indicator containing Geobacillus stearothermophilus spores

Biological indicators containing highly resistant bacterial spores, such as Geobacillus stearothermophilus, are the gold standard for validating sterilization. A successful cycle is confirmed when these spores are killed and fail to grow upon incubation. Chemical indicators and physical readings only confirm that certain conditions were met, not that sterilization was effective.

Question 95: Why is it important to protect bilirubin specimens from light?

Light photodegrades bilirubin, causing falsely decreased results (Correct answer)
Light causes the specimen to hemolyze
Light causes bilirubin to precipitate
Light converts unconjugated bilirubin to conjugated bilirubin

Correct answer: Light photodegrades bilirubin, causing falsely decreased results

Bilirubin is photosensitive and undergoes photoisomerization and photodegradation when exposed to light, particularly UV and fluorescent light. This causes falsely decreased bilirubin results. Specimens should be protected from light by wrapping tubes in foil or using amber-colored tubes.

Question 96: A nurse calls reporting that a patient is having rigors and fever 15 minutes into a red cell transfusion. What are the immediate steps?

Administer epinephrine immediately
STOP the transfusion immediately, keep the IV line open with saline, check patient and unit identification, notify the physician and blood bank, and send required post-reaction specimens (Correct answer)
Slow the transfusion rate
Continue transfusion and give acetaminophen

Correct answer: STOP the transfusion immediately, keep the IV line open with saline, check patient and unit identification, notify the physician and blood bank, and send required post-reaction specimens

The immediate response to any suspected transfusion reaction is: 1) STOP the transfusion, 2) Keep IV open with normal saline, 3) Verify patient and unit identification at the bedside, 4) Notify the physician and blood bank, 5) Send post-reaction blood and urine specimens. The blood bank will perform transfusion reaction investigation including DAT, visual inspection for hemolysis, and repeat ABO/Rh.

Question 97: What is the principle of impedance-based cell counting used in hematology analyzers?

Cells passing through an aperture cause a change in electrical resistance proportional to their volume (Correct answer)
Cells are labeled with fluorescent antibodies and counted by flow cytometry
Cells scatter light at different angles depending on their type
Cells are stained and counted by optical absorption

Correct answer: Cells passing through an aperture cause a change in electrical resistance proportional to their volume

Impedance (Coulter) counting works by detecting the change in electrical resistance as individual blood cells pass through a small aperture between two electrodes. Each cell causes a pulse proportional to its volume, allowing both counting and sizing of cells.

Question 98: What is the difference between a transudate and an exudate in serous body fluids?

Transudates have high protein; exudates have low protein
They are identical in composition
Both require culture for differentiation
Transudates result from hydrostatic/oncotic pressure imbalance (low protein, low LDH, low cells); exudates result from inflammation/infection (high protein, high LDH, high cells) (Correct answer)

Correct answer: Transudates result from hydrostatic/oncotic pressure imbalance (low protein, low LDH, low cells); exudates result from inflammation/infection (high protein, high LDH, high cells)

Transudates are ultrafiltrates resulting from systemic factors (congestive heart failure, cirrhosis, nephrotic syndrome) with low protein (<30 g/L), low LDH, and few cells. Exudates result from local disease processes (infection, malignancy, inflammation) with high protein (>30 g/L), high LDH, and elevated cells. Light's criteria provide the definitive classification.

Question 99: What is phenotype matching and when is it clinically important?

Matching only ABO and Rh(D)
Only required for autologous donations
Extended antigen matching beyond ABO/Rh(D) to prevent alloimmunization in patients requiring chronic transfusions (Correct answer)
Matching based on patient age and weight

Correct answer: Extended antigen matching beyond ABO/Rh(D) to prevent alloimmunization in patients requiring chronic transfusions

Phenotype matching involves selecting donor red cells that match the patient's extended red cell antigen profile (typically Rh (C, c, E, e) and Kell, sometimes Duffy, Kidd, and MNS). It is particularly important for patients with sickle cell disease, thalassemia, and other conditions requiring chronic transfusion to reduce alloimmunization risk.

Question 100: What is the role of the CMLTO Discipline Committee?

To approve new laboratory tests for use in Ontario
To negotiate employment standards for laboratory technologists
To set educational curricula for MLT training programs
To adjudicate allegations of professional misconduct, incompetence, or incapacity against registered members (Correct answer)

Correct answer: To adjudicate allegations of professional misconduct, incompetence, or incapacity against registered members

The CMLTO Discipline Committee adjudicates formal allegations of professional misconduct, incompetence, or incapacity brought against registered MLTs after investigation by the Complaints Committee.

Question 101: In clinical microbiology, what is the purpose of inoculating a blood agar plate and a chocolate agar plate simultaneously when processing a respiratory specimen?

Both media are equivalent — inoculating both ensures redundancy
Chocolate agar inhibits normal flora while blood agar supports all organisms
Blood agar detects beta-hemolytic organisms; chocolate agar supports fastidious organisms like Haemophilus and Neisseria that require growth factors released by heated RBCs (Correct answer)
Blood agar supports fastidious organisms; chocolate agar supports anaerobes only

Correct answer: Blood agar detects beta-hemolytic organisms; chocolate agar supports fastidious organisms like Haemophilus and Neisseria that require growth factors released by heated RBCs

Blood agar supports most bacteria and shows hemolysis patterns; chocolate agar (heated blood agar) releases NAD and hemin from lysed RBCs, supporting fastidious organisms such as Haemophilus influenzae and Neisseria species.

Question 102: Which of the following correctly describes the impact of lipemia on clinical chemistry test results?

Lipemia only affects colorimetric assays and not immunochemical assays
Lipemia has no significant effect if specimens are centrifuged before analysis
Lipemia only affects triglyceride measurements
Lipemia causes interference in multiple assays by light scattering, false volume exclusion, and reagent interference (Correct answer)

Correct answer: Lipemia causes interference in multiple assays by light scattering, false volume exclusion, and reagent interference

Lipemia causes multiple interferences: turbidity affects photometric assays (light scatter), lipid particles displace aqueous volume (pseudohyponatremia with indirect ISE), and lipids can interfere with reagent chemistry.

Question 103: In the coagulation cascade, which pathway is activated by tissue factor released from damaged tissue?

Extrinsic pathway (tissue factor pathway) (Correct answer)
Intrinsic pathway (contact activation)
Common pathway only
Fibrinolytic pathway

Correct answer: Extrinsic pathway (tissue factor pathway)

The extrinsic pathway is initiated by tissue factor (factor III) released from damaged cells outside the blood vessel, which activates factor VII to begin the coagulation cascade.

Question 104: A patient's urine shows many waxy casts, broad casts, and RTE cells. What does this suggest?

Acute urinary tract infection
Severe chronic renal disease with tubular damage and stasis (Correct answer)
Normal urinalysis
Dehydration only

Correct answer: Severe chronic renal disease with tubular damage and stasis

Waxy casts indicate prolonged urinary stasis in damaged tubules. Broad casts ('renal failure casts') form in dilated, damaged collecting ducts. Renal tubular epithelial (RTE) cells indicate active tubular injury. Together, these findings suggest severe chronic kidney disease with ongoing tubular damage and a poor prognosis.

Question 105: What is the purpose of a blood culture incubation system such as the BACTEC or BacT/Alert system?

To visually identify bacterial colonies
To centrifuge blood to separate bacteria from blood cells
To perform antimicrobial susceptibility testing directly
To continuously monitor CO2 production as an indicator of bacterial growth (Correct answer)

Correct answer: To continuously monitor CO2 production as an indicator of bacterial growth

Automated blood culture systems continuously monitor CO2 production in culture bottles, which increases as bacteria metabolize nutrients, signalling a positive culture for the laboratory system.

Question 106: What does the coefficient of variation (CV%) measure in laboratory analytical performance?

The degree of random variation in a method expressed as a percentage of the mean (Correct answer)
The difference between the highest and lowest QC values
The acceptable range of analyte values in a healthy population
The systematic bias between the laboratory and a reference method

Correct answer: The degree of random variation in a method expressed as a percentage of the mean

The CV% (coefficient of variation) expresses imprecision (random variation) as a percentage of the mean: CV% = (SD/Mean) × 100. Lower CV% indicates better precision.

Question 107: Which cytochemical stain is positive in acute myeloid leukemia but negative in acute lymphoblastic leukemia?

Myeloperoxidase (MPO) (Correct answer)
Terminal deoxynucleotidyl transferase (TdT)
Periodic acid-Schiff (PAS)
Non-specific esterase

Correct answer: Myeloperoxidase (MPO)

Myeloperoxidase (MPO) is present in the primary granules of myeloid cells and is positive in most AML subtypes but negative in ALL. It is one of the key cytochemical markers used to distinguish myeloid from lymphoid lineage in acute leukemia, along with Sudan black B and specific esterase.

Question 108: What is gel column technology (gel test) and how does it work in blood banking?

A culture method for growing bacteria
A method for freezing blood products
A method using dextran gel-filled microtubes where agglutinated red cells are trapped in the gel while non-agglutinated cells pass through to the bottom (Correct answer)
A molecular testing method

Correct answer: A method using dextran gel-filled microtubes where agglutinated red cells are trapped in the gel while non-agglutinated cells pass through to the bottom

Gel column technology (DiaMed/Bio-Rad) uses microtubes containing dextran acrylamide gel. After incubation, tubes are centrifuged: agglutinated red cells are trapped in the gel matrix (positive result), while non-agglutinated cells pass through to the bottom (negative result). This standardized method reduces subjective interpretation and is widely used for typing, antibody screening, and crossmatching.

Question 109: Which infection control precaution is implemented when Clostridioides difficile infection is suspected?

Droplet precautions only
Standard precautions only
Contact precautions with hand washing using soap and water (not alcohol-based hand rub) (Correct answer)
Airborne precautions with N95 respirator

Correct answer: Contact precautions with hand washing using soap and water (not alcohol-based hand rub)

C. difficile requires contact precautions including gown and gloves, with hand hygiene using soap and water. Alcohol-based hand sanitizers do NOT kill C. difficile spores. Enhanced environmental cleaning with sporicidal agents (dilute bleach) is also essential as spores can persist on surfaces for months.

Question 110: Which test is used to confirm the presence of a monoclonal protein identified on serum protein electrophoresis?

Free light chain assay
Quantitative immunoglobulins
Immunofixation electrophoresis (IFE) (Correct answer)
Beta-2 microglobulin

Correct answer: Immunofixation electrophoresis (IFE)

Immunofixation electrophoresis (IFE) is the confirmatory test for monoclonal proteins. After electrophoretic separation, specific antisera (anti-IgG, IgA, IgM, kappa, lambda) are applied to identify the heavy and light chain class of the monoclonal immunoglobulin, providing definitive characterization.

Question 111: Which hemoglobin variant migrates in the same position as HbS on alkaline electrophoresis?

HbC
HbE
HbH
HbD and HbG (Correct answer)

Correct answer: HbD and HbG

HbD and HbG migrate in the same position as HbS on alkaline (cellulose acetate) electrophoresis at pH 8.6. To differentiate these variants, a second method such as acid electrophoresis (citrate agar at pH 6.2) or HPLC is required, as they separate differently under acidic conditions.

Question 112: What is the standard approach for donning (putting on) personal protective equipment (PPE) in a medical laboratory?

Eye Protection → Gloves → Gown → Mask
Gown → Mask/Respirator → Eye Protection → Gloves (Correct answer)
Mask → Gloves → Gown → Eye Protection
Gloves → Gown → Mask → Eye Protection

Correct answer: Gown → Mask/Respirator → Eye Protection → Gloves

The recommended sequence for donning PPE is: gown first (to protect clothing), then mask/respirator (to protect respiratory tract), then eye protection, and finally gloves (to protect hands and maintain the rest of the PPE).

Question 113: What are the components of pre-transfusion testing (type and screen)?

Complete blood count and coagulation panel
ABO/Rh typing and antibody screen (indirect antiglobulin test) (Correct answer)
ABO/Rh typing only
Crossmatch only

Correct answer: ABO/Rh typing and antibody screen (indirect antiglobulin test)

Pre-transfusion testing includes: 1) ABO grouping (forward and reverse), 2) Rh(D) typing, and 3) antibody screening (indirect antiglobulin test/IAT) to detect unexpected red cell antibodies. If the antibody screen is positive, antibody identification is performed before crossmatch-compatible blood can be issued.

Question 114: A medical laboratory assistant instructs a patient on collecting a 24-hour urine specimen. Which instruction is a critical part of this procedure?

Keep the collection container at room temperature throughout the 24 hours.
Discard the first morning void, then begin collecting all subsequent urine for 24 hours. (Correct answer)
It is acceptable to miss one or two voids as long as the majority of the urine is collected.
Collect the first morning void on the day the collection starts.

Correct answer: Discard the first morning void, then begin collecting all subsequent urine for 24 hours.

For a 24-hour urine collection, the procedure must start with an empty bladder. Therefore, the patient should void and discard the first morning specimen, note the time, and then collect all urine for the next 24 hours, including the first morning specimen on the following day. The collection container should be kept refrigerated or on ice. Missing any sample can invalidate the test results.

Question 115: A wound culture grows a beta-hemolytic, catalase-negative, gram-positive coccus that is PYR-positive. What is the most likely identification?

Enterococcus faecalis
Group A Streptococcus (Streptococcus pyogenes) (Correct answer)
Staphylococcus aureus
Group B Streptococcus

Correct answer: Group A Streptococcus (Streptococcus pyogenes)

The key features are: beta-hemolytic (GAS, GBS, or Group C/G), catalase-negative (streptococcus/enterococcus, not staphylococcus), gram-positive cocci, and PYR-positive. Among beta-hemolytic streptococci, Group A Streptococcus (S. pyogenes) is PYR-positive while Group B and other groups are PYR-negative.

Question 116: What is the principle of the antimicrobial susceptibility test using the Kirby-Bauer disk diffusion method?

Measuring bacterial growth curves with and without antibiotics
Measuring zones of growth inhibition around antibiotic-impregnated disks on agar (Correct answer)
Detecting antibiotic resistance genes by PCR
Measuring the minimum concentration of antibiotic that inhibits growth

Correct answer: Measuring zones of growth inhibition around antibiotic-impregnated disks on agar

The Kirby-Bauer method measures the diameter of growth inhibition zones around standardized antibiotic disks placed on Mueller-Hinton agar inoculated with a standardized bacterial suspension. Zone sizes are compared to CLSI (or EUCAST) interpretive criteria to classify organisms as susceptible, intermediate, or resistant.

Question 117: Which automated system is commonly used for antimicrobial susceptibility testing and identification in Canadian laboratories?

PCR-based identification only
VITEK 2 or BD Phoenix automated systems (Correct answer)
Manual tube dilution only
Manual Kirby-Bauer only

Correct answer: VITEK 2 or BD Phoenix automated systems

VITEK 2 (bioMérieux) and BD Phoenix are widely used automated systems in Canadian laboratories for both organism identification and antimicrobial susceptibility testing. These systems use miniaturized biochemical reactions and MIC panels, providing results within 6-18 hours. They integrate with laboratory information systems for efficient workflow.

Question 118: In the complement system, which pathway is activated by antigen-antibody complexes?

Lectin pathway
Mannose-binding pathway
Alternative pathway
Classical pathway (Correct answer)

Correct answer: Classical pathway

The classical pathway is activated by antigen-antibody (immune) complexes when IgG or IgM antibodies bind to C1q, initiating the complement cascade.

Question 119: A patient's antibody screen is positive with all three screening cells at the antiglobulin phase. What does this suggest?

Negative antibody screen
Anti-K
Anti-D
Possible warm autoantibody, antibody to a high-frequency antigen, or multiple alloantibodies (Correct answer)

Correct answer: Possible warm autoantibody, antibody to a high-frequency antigen, or multiple alloantibodies

Panreactivity (reactivity with all screening cells) suggests: 1) A warm autoantibody (reacting with a ubiquitous self-antigen), 2) An antibody to a high-frequency antigen (>99% of population), or 3) Multiple alloantibodies together reacting with all cells. An autocontrol (patient serum + patient cells) helps differentiate: if positive, autoantibody is likely; if negative, alloantibody to a high-frequency antigen is more likely.

Question 120: During a peripheral blood film examination, a medical laboratory technologist observes red blood cells with a single pale area and a dense hemoglobin border around the edge. What is the name of these cells?

Schistocytes
Burr cells (echinocytes)
Target cells (codocytes) (Correct answer)
Spherocytes

Correct answer: Target cells (codocytes)

Target cells (codocytes) are RBCs with a bull's-eye appearance — a central dense area and peripheral ring of hemoglobin separated by a pale zone — caused by excess membrane relative to hemoglobin content.

Question 121: A patient's serum glucose is reported as 5.6 mmol/L. What is the equivalent value in mg/dL?

56.0 mg/dL
100.8 mg/dL (Correct answer)
112.0 mg/dL
89.6 mg/dL

Correct answer: 100.8 mg/dL

To convert mmol/L to mg/dL for glucose, multiply by 18.016 (the molecular weight factor). 5.6 × 18.016 = 100.9 mg/dL ≈ 100.8 mg/dL.

Question 122: A post-transfusion DAT is positive with anti-IgG but negative with anti-C3d. The eluate contains anti-c. What type of reaction is this?

Autoimmune hemolytic anemia
Febrile non-hemolytic transfusion reaction
Delayed hemolytic transfusion reaction due to an anamnestic anti-c response (Correct answer)
Bacterial contamination

Correct answer: Delayed hemolytic transfusion reaction due to an anamnestic anti-c response

A positive post-transfusion DAT with anti-IgG and an eluate showing anti-c indicates a delayed hemolytic transfusion reaction. The patient was previously sensitized to the c antigen, and anti-c was undetectable at the time of the pre-transfusion antibody screen. Re-exposure to c-positive donor cells triggered an anamnestic response, producing anti-c that now coats the transfused cells.

Question 123: A patient requires chronic transfusion for sickle cell disease. What special blood bank considerations apply?

Only autologous transfusion
No special considerations
Standard ABO/Rh matching only
Extended phenotype matching (Rh C, c, E, e, and K at minimum) to reduce alloimmunization risk, plus HbS-negative donor units (Correct answer)

Correct answer: Extended phenotype matching (Rh C, c, E, e, and K at minimum) to reduce alloimmunization risk, plus HbS-negative donor units

Sickle cell disease patients have a high alloimmunization rate (25-50%) due to antigen differences between donor (predominantly Caucasian) and recipient (predominantly African descent) populations. Canadian guidelines recommend extended matching for Rh (C, c, E, e) and Kell at minimum. Donor units should be sickle-negative (HbS-negative). Phenotypically similar donors should be actively recruited.

Question 124: Which hormone is measured to assess thyroid function and is produced by the anterior pituitary?

Thyroxine (T4)
Triiodothyronine (T3)
Thyroid-stimulating hormone (TSH) (Correct answer)
Thyroid peroxidase antibody

Correct answer: Thyroid-stimulating hormone (TSH)

TSH is produced by the anterior pituitary gland and is the most sensitive first-line test for thyroid function assessment. TSH levels respond inversely to circulating thyroid hormones through negative feedback, making it an excellent screening test for both hypo- and hyperthyroidism.

Question 125: A patient has hemoglobin 85 g/L, MCV 65 fL, RDW 18%, and serum ferritin 5 µg/L. What is the most likely diagnosis?

Sideroblastic anemia
Iron deficiency anemia (Correct answer)
Beta-thalassemia trait
Anemia of chronic disease

Correct answer: Iron deficiency anemia

The combination of low hemoglobin, microcytosis (MCV 65 fL), elevated RDW (anisocytosis), and very low ferritin (5 µg/L) is classic for iron deficiency anemia. Beta-thalassemia trait typically has a normal RDW and normal ferritin. The low ferritin is the most specific finding for iron deficiency.

Question 126: Which condition is characterized by the presence of target cells (codocytes) on a peripheral blood smear?

Megaloblastic anemia
Thalassemia and liver disease (Correct answer)
Immune hemolytic anemia
Iron deficiency anemia only

Correct answer: Thalassemia and liver disease

Target cells are commonly seen in thalassemia (due to excess membrane relative to hemoglobin content), liver disease (due to altered membrane lipid composition), hemoglobin C disease, and post-splenectomy states. Their bull's-eye appearance results from excess membrane folding.

Question 127: Which molecular method is the gold standard for detecting Chlamydia trachomatis and Neisseria gonorrhoeae?

Gram stain of discharge
Culture on Thayer-Martin agar
Enzyme immunoassay
Nucleic acid amplification test (NAAT) (Correct answer)

Correct answer: Nucleic acid amplification test (NAAT)

NAAT (nucleic acid amplification test) is the gold standard for detecting C. trachomatis and N. gonorrhoeae due to its superior sensitivity and specificity. It can be performed on urine, endocervical, urethral, pharyngeal, and rectal specimens. Culture is still needed for antimicrobial susceptibility testing of N. gonorrhoeae.

Question 128: Excessive centrifugation speed or time is most likely to cause mechanical hemolysis, leading to a falsely elevated result for which of the following analytes?

Sodium
Chloride
Potassium (Correct answer)
Glucose

Correct answer: Potassium

Red blood cells contain a much higher concentration of potassium than blood plasma. When red cells are ruptured (hemolysis) by excessive mechanical force during centrifugation, this intracellular potassium is released into the serum or plasma, causing a significant and false elevation in the measured potassium level.

Question 129: When a medical laboratory technologist refuses to perform a test that they believe may cause patient harm, which professional right is being exercised?

Right to collective bargaining
Right to due process
Right to privacy under PHIPA
Right of conscientious objection or professional refusal (Correct answer)

Correct answer: Right of conscientious objection or professional refusal

MLTs have a professional right to refuse to perform a test or procedure they have legitimate concern may cause patient harm, provided they report the concern through appropriate channels and do not abandon the patient.

Question 130: What does a 'left shift' in the white blood cell differential indicate?

An increase in mature lymphocytes
An increase in eosinophils
An increase in immature granulocytes (bands and metamyelocytes) indicating active infection (Correct answer)
A decrease in all white blood cell types

Correct answer: An increase in immature granulocytes (bands and metamyelocytes) indicating active infection

A left shift refers to an increase in immature granulocytes (particularly band neutrophils, but also metamyelocytes and myelocytes) in peripheral blood. This indicates the bone marrow is releasing cells prematurely in response to increased demand, typically from bacterial infection or inflammation.

Question 131: What is the purpose of the beta-lactamase test in clinical microbiology?

To rapidly detect the production of beta-lactamase enzyme that inactivates penicillins (Correct answer)
To identify the species of a bacterial isolate
To determine the organism's Gram reaction
To test for antimicrobial susceptibility to vancomycin

Correct answer: To rapidly detect the production of beta-lactamase enzyme that inactivates penicillins

The beta-lactamase test (using nitrocefin or acidimetric methods) rapidly detects the production of beta-lactamase enzymes that hydrolyze the beta-lactam ring of penicillins. It is particularly important for Haemophilus influenzae, Neisseria gonorrhoeae, and staphylococci to determine if penicillin-class antibiotics can be used.

Question 132: A peripheral smear shows red blood cells with a central pallor extending over more than one-third of the cell diameter. What does this indicate?

Hypochromia (decreased hemoglobin content) (Correct answer)
Spherocytosis
Polychromasia
Macrocytosis

Correct answer: Hypochromia (decreased hemoglobin content)

Hypochromia is characterized by increased central pallor (>1/3 of cell diameter) indicating decreased hemoglobin content. This is commonly seen in iron deficiency anemia and thalassemia. The MCH and MCHC values will also be decreased. It reflects insufficient hemoglobin filling the red blood cell.

Question 133: What is the clinical significance of an elevated serum amylase level?

Hypothyroidism
Acute pancreatitis (Correct answer)
Congestive heart failure
Renal failure

Correct answer: Acute pancreatitis

Elevated serum amylase is most commonly associated with acute pancreatitis. Amylase is released from damaged pancreatic acinar cells into the bloodstream. However, amylase can also be elevated in other conditions such as salivary gland disorders and intestinal obstruction.

Question 134: An MLT is asked by a colleague to process a stat sample for the colleague's own family member without a physician's requisition. What is the most appropriate response?

Process the sample with a retroactive requisition
Decline, as this violates professional and ethical standards (Correct answer)
Process the sample but flag it in the system
Process the sample as a professional courtesy

Correct answer: Decline, as this violates professional and ethical standards

Processing specimens without a valid physician's requisition violates laboratory policy, professional standards, and the ethical principle of maintaining professional boundaries.

Question 135: What does the term 'evidence-based practice' mean for a medical laboratory technologist in Ontario?

Avoiding experimental techniques until they are approved by CMLTO
Performing the same procedures as all other Ontario laboratories without variation
Using only tests that have been published in peer-reviewed journals
Integrating the best available evidence from research with professional judgment and patient context to guide practice decisions (Correct answer)

Correct answer: Integrating the best available evidence from research with professional judgment and patient context to guide practice decisions

Evidence-based practice means integrating the best available research evidence with professional knowledge, experience, and the specific patient context to make optimal practice decisions.

Question 136: What is the INR and why was it developed?

International Normalized Ratio; to standardize PT results across laboratories using different thromboplastin reagents (Correct answer)
Initial Neutrophil Reaction; to standardize white cell differential counts
International Normalized Range; to define universal reference ranges
Intrinsic Normalization Rate; to standardize aPTT results

Correct answer: International Normalized Ratio; to standardize PT results across laboratories using different thromboplastin reagents

The INR (International Normalized Ratio) was developed to standardize PT results across laboratories using thromboplastin reagents with different sensitivities. The INR = (patient PT/mean normal PT)^ISI, where ISI is the International Sensitivity Index of the thromboplastin reagent.

Question 137: Which cell type is the precursor to platelets?

Monoblast
Myeloblast
Reticulocyte
Megakaryocyte (Correct answer)

Correct answer: Megakaryocyte

Megakaryocytes are the large bone marrow cells that produce platelets through cytoplasmic fragmentation. Each megakaryocyte can produce approximately 1,000-3,000 platelets. Thrombopoietin (TPO) is the primary growth factor regulating megakaryocyte development and platelet production.

Question 138: Which organism is the most common cause of bacterial meningitis in Canadian adults?

Haemophilus influenzae type b
Streptococcus pneumoniae (Correct answer)
Listeria monocytogenes
Escherichia coli

Correct answer: Streptococcus pneumoniae

Streptococcus pneumoniae is the most common cause of bacterial meningitis in adults in Canada. It appears as gram-positive lancet-shaped diplococci on CSF Gram stain. Since the introduction of Hib vaccine, H. influenzae meningitis has decreased dramatically. In neonates, Group B Streptococcus and E. coli are more common.

Question 139: What is the trichrome stain used for in parasitology?

Identifying fungal hyphae
Detecting acid-fast organisms
Permanent staining of intestinal protozoan trophozoites and cysts in stool specimens (Correct answer)
Staining malaria parasites in blood

Correct answer: Permanent staining of intestinal protozoan trophozoites and cysts in stool specimens

The trichrome stain is a permanent stain for identifying intestinal protozoa (such as Entamoeba histolytica, Giardia lamblia, and Dientamoeba fragilis) in stool specimens preserved in polyvinyl alcohol (PVA) or SAF fixative. It provides excellent detail of nuclear and cytoplasmic features essential for accurate species identification.

Question 140: What is the universal plasma donor type?

Type AB (Correct answer)
Type B
Type O
Type A

Correct answer: Type AB

Type AB plasma is the universal plasma donor because it contains no anti-A or anti-B antibodies, making it safe for recipients of any ABO type. This is the opposite of red cell donation, where O is universal. AB plasma is used in emergency situations and for patients with unknown blood types requiring plasma transfusion.

Question 141: What is the significance of finding white blood cell (WBC) casts in urine?

They are a normal finding
They indicate renal parenchymal inflammation, typically pyelonephritis or interstitial nephritis (Correct answer)
They indicate urethral infection
They indicate bladder infection

Correct answer: They indicate renal parenchymal inflammation, typically pyelonephritis or interstitial nephritis

WBC casts localize inflammation to the kidney (renal tubules), distinguishing upper urinary tract infection (pyelonephritis) or interstitial nephritis from lower UTI (cystitis). WBCs trapped in Tamm-Horsfall protein matrix form these casts within the renal tubules. Their presence warrants further investigation of renal parenchymal disease.

Question 142: A urine sample from a patient on the antibiotic nitrofurantoin shows a brown/dark colour. The dipstick is negative for blood. What explains the colour?

Drug-induced colour change — nitrofurantoin metabolites produce brown/rust-coloured urine as a known harmless side effect (Correct answer)
Myoglobinuria
Hematuria
Bilirubinuria

Correct answer: Drug-induced colour change — nitrofurantoin metabolites produce brown/rust-coloured urine as a known harmless side effect

Several medications cause distinctive urine colour changes: nitrofurantoin (brown/rust), rifampin (red-orange), phenazopyridine (bright orange), and metronidazole (dark/red-brown). These are harmless metabolite effects. The negative blood dipstick rules out hematuria. Patient medication history is essential when investigating abnormal urine colour.

Question 143: The MHC class II molecules present antigen to which subset of T lymphocytes?

Natural killer cells
Regulatory T cells only
CD4+ helper T cells (Correct answer)
CD8+ cytotoxic T cells

Correct answer: CD4+ helper T cells

MHC class II molecules on antigen-presenting cells present exogenous peptide antigens to CD4+ helper T cells via the CD4 co-receptor, initiating the adaptive immune response.

Question 144: What is heparin-induced thrombocytopenia (HIT) type II?

A genetic platelet disorder worsened by heparin
A benign, transient drop in platelets within the first 2 days of heparin
An allergic reaction to heparin causing rash
An immune-mediated condition causing platelet activation, thrombocytopenia, and paradoxical thrombosis (Correct answer)

Correct answer: An immune-mediated condition causing platelet activation, thrombocytopenia, and paradoxical thrombosis

HIT type II is a serious immune-mediated condition where antibodies against heparin-platelet factor 4 (PF4) complexes activate platelets, causing both thrombocytopenia (platelet count drop >50%) and a paradoxical prothrombotic state. It typically occurs 5-14 days after heparin exposure and requires immediate heparin cessation and alternative anticoagulation.

Question 145: What does an immature platelet fraction (IPF) help assess?

The rate of platelet production by the bone marrow (Correct answer)
Platelet antibodies
Platelet aggregation response
Platelet function

Correct answer: The rate of platelet production by the bone marrow

The immature platelet fraction measures the percentage of newly released (reticulated) platelets, analogous to the reticulocyte count for red blood cells. An elevated IPF with thrombocytopenia indicates increased platelet destruction (ITP, DIC), while a low IPF suggests decreased bone marrow production.

Question 146: Which of the following activities is considered part of Quality Assurance (QA) but not Quality Control (QC) in a clinical laboratory setting?

Reviewing and updating the laboratory's standard operating procedures (SOPs). (Correct answer)
Calibrating a new reagent lot before use.
Performing preventative maintenance on an instrument.
Running daily control samples on an analyzer.

Correct answer: Reviewing and updating the laboratory's standard operating procedures (SOPs).

Quality Assurance (QA) is a broad, proactive process that encompasses all systems and procedures to ensure quality results, including documentation and training. [2, 3] Reviewing and updating SOPs is a key QA activity that ensures processes are current and correct. [2] In contrast, Quality Control (QC) refers to the specific, operational techniques and activities used to fulfill requirements for quality, such as running controls, performing maintenance, and calibrating reagents, which are all part of the analytical process. [2, 4]

Question 147: What is the primary buffer system in human blood plasma?

Hemoglobin buffer system
Phosphate buffer system
Protein buffer system
Bicarbonate-carbonic acid buffer system (Correct answer)

Correct answer: Bicarbonate-carbonic acid buffer system

The bicarbonate-carbonic acid buffer system is the primary buffer in blood plasma, maintaining pH between 7.35 and 7.45. This system is regulated by both the lungs (CO2 excretion) and kidneys (bicarbonate reabsorption), making it highly effective at maintaining acid-base balance.

Question 148: A medical laboratory assistant receives an unlabeled tube of blood for a complete blood count (CBC). The requisition form is present and correctly filled out. What is the most appropriate immediate action?

Process the sample and add a note to the report that the initial specimen was unlabeled.
Reject the specimen and request a new, properly labeled sample be collected. (Correct answer)
Label the tube with the patient's information from the requisition and process the sample.
Ask a coworker for their opinion on what to do with the specimen.

Correct answer: Reject the specimen and request a new, properly labeled sample be collected.

Specimen integrity and correct patient identification are paramount for patient safety. An unlabeled specimen is a critical pre-analytical error that cannot be corrected after the fact. [23] The only acceptable action is to reject the specimen and notify the appropriate personnel to recollect a new, properly labeled sample to ensure the results are linked to the correct patient. [22]

Question 149: A patient with HIV has CD4 count below 200 cells/µL and presents with chronic watery diarrhea. Modified acid-fast stain of stool shows small round pink oocysts (4-6 µm). What is the diagnosis?

Giardiasis
Cyclosporiasis
Cryptosporidiosis (Correct answer)
Isosporiasis

Correct answer: Cryptosporidiosis

Cryptosporidium oocysts are 4-6 µm, round, and stain variably pink with modified acid-fast stain. Cryptosporidiosis causes chronic, potentially life-threatening watery diarrhea in severely immunocompromised patients (CD4 <200). Cyclospora oocysts are larger (8-10 µm) and stain variably. Antiretroviral therapy to restore CD4 count is the most effective treatment.

Question 150: A urine specimen from a child has a positive dipstick for blood and protein. Microscopy shows RBC casts and dysmorphic red blood cells. Serum complement C3 is low. What diagnosis should be suspected?

Bladder trauma
Urinary tract infection
Nephrotic syndrome
Post-streptococcal glomerulonephritis (Correct answer)

Correct answer: Post-streptococcal glomerulonephritis

RBC casts (proving glomerular origin of hematuria), dysmorphic RBCs, proteinuria, and low serum complement (C3 consumption via the alternative pathway) in a child are classic for post-streptococcal glomerulonephritis. This immune-complex mediated disease typically follows a group A streptococcal pharyngitis or skin infection by 1-3 weeks. ASO titer and anti-DNase B confirm recent streptococcal infection.

Question 151: What is the antibody screening cell (screening cells) composition and why are they group O?

Screening cells can be any ABO type
Group O cells have more antigens than other types
Group O cells are easier to store
Group O cells lack A and B antigens, preventing ABO antibodies from masking other clinically significant antibodies (Correct answer)

Correct answer: Group O cells lack A and B antigens, preventing ABO antibodies from masking other clinically significant antibodies

Antibody screening cells are always group O to avoid reactions with naturally occurring anti-A and anti-B (which are expected and clinically managed through ABO-compatible crossmatch). Using group O cells ensures that only unexpected, potentially clinically significant antibodies are detected. Screening cells express a wide range of clinically significant antigens.

MLPAO MLA/T Certification Exam

The MLPAO MLA/T certification exam tests medical laboratory assistants/technicians in clinical chemistry, hematology, microbiology, transfusion medicine, specimen collection, laboratory safety, and professional practice.

150

Questions

180 min

Time Limit

60%

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