Mixed Deck — All Laboratory Science Topics Flashcards
100 cards from real Laboratory Science practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 20 Mixed Deck — All Laboratory Science Topics flashcards as text
What is the purpose of a streak plate technique in microbiology?
Answer: Isolate individual bacterial colonies from a mixed culture
The streak plate technique dilutes bacteria across successive sectors, producing isolated single colonies from a mixed specimen for pure culture isolation and identification.
What is the Henderson-Hasselbalch equation used for in clinical chemistry?
Answer: Relating blood pH to bicarbonate and dissolved CO₂ concentration
The Henderson-Hasselbalch equation (pH = pKa + log[HCO₃⁻/0.0307×pCO₂]) describes the relationship between pH, bicarbonate, and CO₂, critical for interpreting acid-base disorders.
Blood cultures are typically incubated for how many days before being reported as negative?
Answer: 5 days
Most clinical blood cultures are incubated for 5 days in automated systems (e.g., BACTEC), which is sufficient to detect the vast majority of clinically significant bacteremia.
Which lipoprotein fraction is considered 'good cholesterol' due to its cardioprotective role?
Answer: HDL (high-density lipoprotein)
HDL transports cholesterol from peripheral tissues back to the liver for excretion (reverse cholesterol transport), and higher HDL levels are associated with reduced cardiovascular risk.
Which acute transfusion reaction is the most severe and potentially life-threatening?
Answer: Acute hemolytic transfusion reaction
Acute hemolytic transfusion reactions, most often caused by ABO incompatibility, trigger complement activation that can lead to DIC, renal failure, and death.
Which culture medium is used for isolating Neisseria gonorrhoeae from clinical specimens?
Answer: Thayer-Martin (modified) agar
Thayer-Martin agar is a selective medium containing antibiotics (vancomycin, colistin, nystatin) that suppress normal flora while allowing N. gonorrhoeae to grow.
Which rapid test is used for presumptive identification of group A streptococcal pharyngitis in the lab?
Answer: Lateral flow immunoassay antigen detection (rapid strep test)
Rapid strep tests use lateral flow immunoassay to detect Group A Strep carbohydrate antigen directly from throat swabs in minutes, guiding immediate treatment decisions.
Which biosafety level (BSL) is required for working with agents that pose a moderate risk to personnel but low risk to the community?
Answer: BSL-2
BSL-2 is used for work with agents of moderate potential hazard to personnel and the environment, such as Hepatitis B virus.
What is a direct antiglobulin test (DAT) used to detect?
Answer: Antibodies or complement bound directly to the patient's red blood cells
The DAT (direct Coombs test) detects IgG or complement proteins already coating the patient's RBCs in vivo, used to diagnose autoimmune hemolytic anemia and hemolytic disease of the newborn.
What does a zone of inhibition in a Kirby-Bauer disk diffusion test represent?
Answer: Area where antibiotic has diffused and inhibited bacterial growth
In Kirby-Bauer testing, antibiotics diffuse outward from disks; the zone of inhibition (no growth) diameter is compared to CLSI breakpoints to determine susceptibility (S/I/R).
What is the rheumatoid factor (RF) test measuring?
Answer: IgM autoantibodies directed against the Fc region of IgG
Rheumatoid factor is typically IgM autoantibodies against the Fc region of IgG; elevated RF supports rheumatoid arthritis diagnosis but is not specific (also elevated in infections and other autoimmune diseases).
What does SDS stand for in laboratory chemical safety?
Answer: Safety Data Sheet
A Safety Data Sheet (SDS) provides detailed information about a chemical's properties, hazards, handling, storage, and emergency procedures.
What is the principle behind the precipitin reaction in immunology testing?
Answer: Antigen and antibody in optimal proportions form insoluble immune complexes that precipitate out of solution
Precipitin reactions occur when soluble antigens and antibodies combine in equivalence zone proportions to form large insoluble lattice complexes that precipitate, visible as a line or band in gel diffusion assays.
Which additive solution extends the shelf life of red blood cell units to 42 days?
Answer: AS-1 (Additive Solution-1/Adsol)
Additive solutions such as AS-1 (Adsol) provide adenine, glucose, and saline that extend RBC shelf life to 42 days.
Which complement pathway is activated by antigen-antibody complexes (IgG or IgM)?
Answer: Classical pathway
The classical complement pathway is initiated by C1q binding to Fc regions of antigen-bound IgG or IgM, triggering the C1-C2-C4 cascade and ultimately forming the membrane attack complex.
What is the primary purpose of irradiating blood products before transfusion?
Answer: Prevent transfusion-associated graft-versus-host disease (TA-GvHD)
Irradiation inactivates donor T-lymphocytes, preventing them from engrafting and attacking tissues in immunocompromised recipients (TA-GvHD).
The major crossmatch tests compatibility between which two components?
Answer: Recipient serum and donor red cells
The major crossmatch tests recipient serum against donor red cells to detect antibodies that could destroy the transfused cells.
HLA (Human Leukocyte Antigen) typing is most critical for which procedure?
Answer: Organ and stem cell transplantation compatibility
HLA antigens on transplanted organ cells are recognized as foreign by the recipient's immune system; HLA matching between donor and recipient minimizes rejection and graft-versus-host disease.
What is the clinical significance of a PSA (prostate-specific antigen) level greater than 10 ng/mL?
Answer: Highly suspicious for prostate cancer, requiring further workup
PSA >10 ng/mL significantly increases the probability of prostate cancer and warrants biopsy; however, PSA elevation is not diagnostic alone (also elevated in BPH and prostatitis).
What is the reference range for fasting blood glucose in a non-diabetic adult?
Answer: 70–99 mg/dL
Normal fasting plasma glucose is 70–99 mg/dL; values of 100–125 mg/dL indicate prediabetes, and ≥126 mg/dL on two occasions diagnoses diabetes mellitus.