ASPT Specimen Handling and Processing 2 — Questions and Answers
Question 1: What is the maximum time a whole blood specimen should remain at room temperature before centrifugation if a serum specimen is needed?
- 15 minutes
- 30 minutes
- 2 hours (Correct answer)
- 4 hours
Correct answer: 2 hours
Most serum specimens should be centrifuged within 2 hours of collection to prevent cellular metabolism from altering analyte values.
Question 2: Which tube additive can cause falsely elevated potassium results if the specimen is hemolyzed?
- Sodium citrate
- EDTA (Correct answer)
- Heparin
- Sodium fluoride
Correct answer: EDTA
EDTA chelates calcium and can cause potassium to leak from red blood cells when hemolysis occurs, falsely elevating potassium levels.
Question 3: A specimen labeled 'STAT' arrives at the lab at the same time as a routine specimen. Which specimen should be processed first?
- The routine specimen, as it was collected earlier
- The STAT specimen, as it has higher priority (Correct answer)
- Process them simultaneously
- Contact the ordering physician for guidance
Correct answer: The STAT specimen, as it has higher priority
STAT specimens always take priority over routine specimens because they indicate urgent patient care needs.
Question 4: What is the purpose of inverting a blood collection tube after collection?
- To activate clotting
- To mix the additive with blood (Correct answer)
- To prevent hemolysis
- To increase specimen volume
Correct answer: To mix the additive with blood
Gentle inversion mixes the tube additive (anticoagulant, gel separator, etc.) thoroughly with the blood specimen.
Question 5: Which specimen storage condition is required for cold agglutinin testing?
- Refrigerate at 2–8°C immediately
- Keep warm at 37°C until testing (Correct answer)
- Store at room temperature for 24 hours
- Freeze at –20°C immediately
Correct answer: Keep warm at 37°C until testing
Cold agglutinin specimens must be kept warm (37°C) because cold temperatures cause the antibodies to bind and give false results.
Question 6: How many times should a tube with EDTA be inverted after collection?
- 2–3 times
- 5–6 times
- 8–10 times (Correct answer)
- 15–20 times
Correct answer: 8–10 times
EDTA tubes should be inverted 8–10 times to ensure adequate mixing of the anticoagulant with blood without causing hemolysis.
Question 7: What does a gel separator in an SST tube do after centrifugation?
- Prevents clot formation
- Forms a barrier between serum and cells (Correct answer)
- Accelerates clotting
- Prevents specimen evaporation
Correct answer: Forms a barrier between serum and cells
The thixotropic gel migrates during centrifugation to form a stable physical barrier between the serum layer and the clot.
ASPT Specimen Handling and Processing 2
What is the maximum time a whole blood specimen should remain at room temperature before centrifugation if a serum specimen is needed?