NHA Certified Phlebotomy Technician (CPT)Collection RoutineHard
A phlebotomy technician is collecting blood for a STAT electrolyte panel and a CBC. According to the CLSI order of draw, which tube should be drawn first?
- AGreen top (lithium heparin) tube
- BLight blue top tube
- CLavender top tube
- DRed top tube
Show answer & explanationAnswer & explanation
Correct answer: A. Green top (lithium heparin) tube
According to the CLSI order of draw, blood cultures (if ordered) come first, followed by coagulation tubes (light blue), then serum tubes (red/gold), then heparin tubes (green), and finally EDTA tubes (lavender). For a STAT electrolyte panel, a green top (heparin) tube would be drawn before a lavender top (EDTA) tube for a CBC.
Why the other options are wrong
- B. Light blue top (sodium citrate) tubes are for coagulation studies and are drawn before green or lavender tubes, but are not listed in this scenario as being needed.
- C. Lavender top (EDTA) tubes are drawn after heparin tubes in the CLSI order of draw.
- D. Red top tubes are for serum tests and are typically drawn before green or lavender tubes, but a STAT electrolyte panel is often collected in a green top tube for plasma.
CLSI Order of Draw
The standardized sequence for collecting blood in multiple tubes to prevent additive carryover and ensure accurate test results.
- Blood cultures (sterile specimen) first.
- Light blue (coagulation) second.
- Red/Gold (serum/SST) third.
- Green (heparin) fourth.
- Lavender (EDTA) fifth.
- Gray (glucose/lactate) sixth.
Memory trick: Remember 'Stop Light Red Stay Put Green Light Go'