NHA Certified Phlebotomy Technician (CPT)Collection RoutineEasy
A phlebotomy technician is preparing to collect a blood specimen for a prothrombin time (PT) test. Which of the following tubes should the technician use?
- ALavender top tube
- BLight blue top tube
- CRed top tube
- DGray top tube
Show answer & explanationAnswer & explanation
Correct answer: B. Light blue top tube
A prothrombin time (PT) test, which measures the time it takes for blood plasma to clot, requires a light blue top tube containing sodium citrate as an anticoagulant. Sodium citrate prevents clotting by binding calcium, preserving the coagulation factors for accurate testing.
Why the other options are wrong
- A. Lavender top tubes contain EDTA and are used for hematology tests like CBC.
- C. Red top tubes are plain tubes or contain clot activators and are used for serum chemistry or blood banking.
- D. Gray top tubes contain sodium fluoride and potassium oxalate and are used for glucose and lactate testing.
Light Blue Top Tube
A vacuum blood collection tube identified by its light blue cap, containing sodium citrate as an anticoagulant.
- Additive: Sodium Citrate.
- Mechanism: Binds calcium to prevent clotting.
- Primary Use: Coagulation studies (PT, PTT, INR).
Memory trick: PT/PTT: Light Blue for Coagulation's Clue.