NHA Certified Phlebotomy Technician (CPT)Collection RoutineMedium
A phlebotomy technician needs to collect a specimen for a Coagulation Panel (PT/INR, PTT). Which of the following evacuated tubes should be used?
- ALight blue top tube.
- BRed top tube.
- CGray top tube.
- DLavender top tube.
Show answer & explanationAnswer & explanation
Correct answer: A. Light blue top tube.
Coagulation studies like PT/INR and PTT require a light blue top tube, which contains sodium citrate as an anticoagulant. This additive prevents clotting by binding calcium, preserving the coagulation factors for testing.
Why the other options are wrong
- B. Red top tubes are plain and used for serum collection (e.g., blood banking, chemistry), allowing blood to clot.
- C. Gray top tubes contain sodium fluoride and potassium oxalate, used for glucose and alcohol levels, preventing glycolysis.
- D. Lavender top tubes contain EDTA and are used for hematology tests like CBC, not coagulation studies.
Light Blue Top Tube
The light blue top tube contains sodium citrate, an anticoagulant that prevents blood clotting by binding calcium, making it suitable for coagulation studies.
- Additive: Sodium Citrate.
- Common tests: PT, PTT, INR, D-dimer.
- Requires a 9:1 blood-to-anticoagulant ratio.
Memory trick: Colorful caps, specific jobs, know your test!