NCCT National Certified Phlebotomy Technician MCQ 2 — Questions and Answers
Question 1: Which of the following is the correct order of draw when using the evacuated tube system?
- Blood cultures, light blue, red/SST, green, lavender, gray (Correct answer)
- Lavender, green, red/SST, light blue, blood cultures, gray
- Red/SST, blood cultures, light blue, green, lavender, gray
- Light blue, blood cultures, red/SST, lavender, green, gray
Correct answer: Blood cultures, light blue, red/SST, green, lavender, gray
The correct CLSI order of draw is: blood cultures (yellow SPS), light blue (citrate), red/SST (serum), green (heparin), lavender (EDTA), gray (oxalate/fluoride).
The CLSI order of draw prevents additive carryover between tubes. The sequence is: blood cultures/SPS, coagulation (light blue/citrate), serum tubes (red, gold SST), heparin (green), EDTA (lavender), glycolytic inhibitor (gray).
Question 2: A patient's PT (prothrombin time) result is prolonged. Which pathway of the coagulation cascade is primarily being evaluated?
- Intrinsic pathway
- Extrinsic pathway (Correct answer)
- Common pathway only
- Fibrinolytic pathway
Correct answer: Extrinsic pathway
PT primarily evaluates the extrinsic pathway (Factor VII) and the common pathway (Factors X, V, II, and fibrinogen) of the coagulation cascade.
The PT test measures the time for plasma to clot after adding tissue factor (thromboplastin) and calcium. Tissue factor activates the extrinsic pathway by converting Factor VII to VIIa. PT is prolonged by warfarin therapy, liver disease, or vitamin K deficiency.
Question 3: Which test requires blood to be collected in a sodium fluoride/potassium oxalate (gray-top) tube?
- Complete blood count
- Prothrombin time
- Blood glucose (Correct answer)
- Blood culture
Correct answer: Blood glucose
Gray-top tubes containing sodium fluoride and potassium oxalate are specifically designed for glucose testing because sodium fluoride inhibits glycolysis.
Sodium fluoride in gray-top tubes inhibits the enzyme enolase in the glycolytic pathway, preventing blood cells from metabolizing glucose after collection. Without this inhibitor, blood glucose decreases approximately 5-7% per hour at room temperature.
Question 4: An Allen test is performed before collecting blood from which site?
- Antecubital fossa veins
- Dorsal hand veins
- Radial artery (Correct answer)
- Femoral vein
Correct answer: Radial artery
The Allen test evaluates collateral circulation to the hand via the ulnar artery before a radial artery puncture.
The Allen test is mandatory before radial artery puncture for arterial blood gas collection. It verifies that the ulnar artery provides adequate collateral blood flow to the hand through the palmar arch. If the hand remains pale after releasing the ulnar artery (negative Allen test), the radial artery should NOT be punctured on that side.
Question 5: Which of the following conditions would be a contraindication for blood collection from a specific arm?
- The patient had breakfast 2 hours ago
- An IV is running in that arm (Correct answer)
- The patient exercised that morning
- The patient is right-handed
Correct answer: An IV is running in that arm
An arm with an active IV line is contraindicated for blood collection because IV fluids will contaminate the specimen and produce inaccurate results.
Blood should not be drawn from an arm with an active IV because the IV fluid dilutes blood components and adds exogenous substances to the specimen. Other contraindications include mastectomy on that side, AV fistula or graft for dialysis, and burned or scarred areas.
Question 6: What is the most critical step in preventing preanalytical errors in phlebotomy?
- Using the most expensive equipment available
- Correct patient identification using two identifiers (Correct answer)
- Drawing the maximum amount of blood possible
- Completing the blood draw as quickly as possible
Correct answer: Correct patient identification using two identifiers
Correct patient identification using at least two identifiers is the single most important step in preventing preanalytical errors.
Wrong patient blood draw is the most serious preanalytical error because it can lead to fatal hemolytic transfusion reactions, incorrect medication dosing, and missed diagnoses. Two-identifier verification is the primary prevention strategy.
NCCT National Certified Phlebotomy Technician MCQ 2
Which of the following is the correct order of draw when using the evacuated tube system?