NHA Certified Phlebotomy Technician (CPT)Specimen HandlingHard
A phlebotomy technician is preparing to process a specimen for a blood ammonia level. Which of the following is the most critical step to maintain specimen integrity?
- AAllowing the specimen to clot for 30 minutes.
- BCentrifuging the specimen at high speed for 15 minutes.
- CInverting the tube 8-10 times gently.
- DPlacing the tube on ice immediately after collection.
Show answer & explanationAnswer & explanation
Correct answer: D. Placing the tube on ice immediately after collection.
Blood ammonia levels increase rapidly at room temperature due to cellular metabolism. Placing the specimen on ice immediately slows down this metabolic process, preserving the ammonia concentration for accurate testing.
Why the other options are wrong
- A. Ammonia specimens are typically collected in anticoagulant tubes (e.g., EDTA, heparin) and do not require clotting.
- B. Centrifugation is required for plasma separation, but the immediate chilling step is more critical for ammonia integrity than the specific centrifugation parameters.
- C. While gentle inversion is needed for anticoagulant tubes, it's not the most critical step for ammonia compared to chilling.
Ammonia Specimen Handling
Blood ammonia levels are highly sensitive to temperature and cellular metabolism. Immediate chilling on ice is essential to prevent falsely elevated results.
- Collect in EDTA or heparin tube.
- Place on ice immediately.
- Centrifuge and separate plasma quickly (within 15-30 mins).
Memory trick: Ammonia's a hothead, keep it cold or it's dead!