ASCP Phlebotomy 2 — Questions and Answers
Question 1: What blood-to-anticoagulant ratio is required for sodium citrate (light-blue top) tubes used in coagulation studies?
- 1:1
- 4:1
- 9:1 (Correct answer)
- 10:1
Correct answer: 9:1
A 9:1 blood-to-citrate ratio (9 parts blood to 1 part sodium citrate) is required; underfilling dilutes the anticoagulant and artificially prolongs clotting times.
Question 2: A patient has a hematocrit of 62%. How should the phlebotomist adjust sodium citrate tube collection?
- No adjustment needed
- Use a larger sodium citrate tube
- Collect less blood to maintain the correct blood-to-citrate ratio (Correct answer)
- Add extra sodium citrate to compensate
Correct answer: Collect less blood to maintain the correct blood-to-citrate ratio
In patients with hematocrit >55%, less blood is drawn because the reduced plasma volume requires a smaller blood volume to maintain the 9:1 ratio with citrate.
Question 3: Which additive is found in a gray-top blood collection tube?
- EDTA
- Sodium heparin
- Sodium fluoride/potassium oxalate (Correct answer)
- Sodium citrate
Correct answer: Sodium fluoride/potassium oxalate
Gray-top tubes contain sodium fluoride (glycolysis inhibitor) and potassium oxalate (anticoagulant), used for glucose and lactate specimens requiring glycolysis inhibition.
Question 4: How many times should a serum separator tube (SST/gold or red-gold) be inverted immediately after collection?
- 0 times — do not mix
- 3–4 times
- 5–6 times (Correct answer)
- 10 times
Correct answer: 5–6 times
SST tubes should be inverted 5–6 times to ensure the clot activator (silica particles) mixes thoroughly with the blood without causing hemolysis.
Question 5: Which of the following specimens must be placed in ice water slurry immediately after collection?
- Complete blood count (CBC)
- Arterial blood gas (ABG) (Correct answer)
- Blood culture
- Prothrombin time (PT)
Correct answer: Arterial blood gas (ABG)
ABG specimens must be chilled immediately because ongoing cellular metabolism alters pH, pO2, and pCO2 values within minutes at room temperature.
Question 6: How long should a serum specimen without a clot activator be allowed to clot before centrifugation?
- 5–10 minutes
- 15–20 minutes
- 30–60 minutes (Correct answer)
- 90–120 minutes
Correct answer: 30–60 minutes
Plain serum tubes should clot for 30–60 minutes at room temperature to allow complete fibrin polymerization before centrifugation; incomplete clotting causes fibrin strands in the serum.
Question 7: A specimen is discovered to be labeled with the wrong patient's name after analysis. What is the correct action?
- Report results with a notation about the labeling error
- Relabel the tube with the correct patient name and reprocess
- Reject the specimen and collect a new properly labeled sample after notifying the provider (Correct answer)
- Run the test again on the same specimen before reporting
Correct answer: Reject the specimen and collect a new properly labeled sample after notifying the provider
Mislabeled specimens are a critical patient safety issue; they must be rejected, the provider notified, and a new, correctly labeled specimen obtained.
ASCP Phlebotomy 2
What blood-to-anticoagulant ratio is required for sodium citrate (light-blue top) tubes used in coagulation studies?