NHA Certified Phlebotomy Technician (CPT)Specimen HandlingMedium
A phlebotomy technician is preparing to process a serum tube for a chemistry test. After collection, how long should the tube typically be allowed to clot at room temperature before centrifugation?
- A1 to 5 minutes.
- B30 to 60 minutes.
- C2 to 4 hours.
- DImmediately centrifuge upon collection.
Show answer & explanationAnswer & explanation
Correct answer: B. 30 to 60 minutes.
Serum tubes (plain or with clot activators) require adequate time for complete clotting before centrifugation. A typical timeframe for clotting at room temperature is 30 to 60 minutes to ensure proper separation of serum from the cellular components.
Why the other options are wrong
- A. 1-5 minutes is generally insufficient for complete clotting, even with clot activators.
- C. Allowing the tube to clot for 2-4 hours is excessive and can lead to analyte degradation, especially for time-sensitive tests.
- D. Immediate centrifugation would result in an incomplete clot and poor serum separation, potentially leading to fibrin strands.
Serum Clotting Time
For serum tubes, a waiting period of 30-60 minutes at room temperature is typically required for complete clot formation before centrifugation to ensure proper separation of serum.
- Inadequate clotting causes fibrin strands.
- Clot activators speed up the process.
- Too long can degrade analytes.
Memory trick: Clotting: Thirty to Sixty, then Spin it Neatly.