NHA Certified Phlebotomy Technician (CPT)Collection RoutineEasy
A phlebotomy technician needs to collect a blood specimen for a complete blood count (CBC) and a prothrombin time (PT). Which of the following is the correct order of draw for these tubes?
- ALight blue top, red top
- BLight blue top, lavender top
- CRed top, lavender top
- DLavender top, light blue top
Show answer & explanationAnswer & explanation
Correct answer: B. Light blue top, lavender top
According to the CLSI order of draw, the light blue top tube (for PT) comes before the lavender top tube (for CBC) to prevent contamination of the coagulation factors by EDTA.
Why the other options are wrong
- A. Red tops are typically drawn after light blue, but a CBC is also needed, which is a lavender top.
- C. Red tops are for serum; lavender tops are for whole blood, but the light blue tube must precede both for PT.
- D. This order is incorrect; EDTA from the lavender tube can interfere with coagulation tests.
Order of Draw (CLSI)
The specific sequence in which blood collection tubes are filled during venipuncture to prevent cross-contamination of additives between tubes, ensuring accurate test results.
- Standardized by CLSI (Clinical and Laboratory Standards Institute)
- Prevents additive carryover
- Ensures accurate lab results
- Common sequence: Blood Cultures, Light Blue, Red/Gold, Green, Lavender, Gray
Memory trick: BLGRGLG: 'Blood Cultures' 'Light Blue' 'Red/Gold' 'Green' 'Lavender' 'Gray'… 'Go'!