NHA Certified Phlebotomy Technician (CPT)Collection RoutineMedium
A phlebotomy technician is collecting a blood specimen for a STAT electrolyte panel and a routine complete blood count (CBC). Which of the following tubes should be drawn first, according to the CLSI order of draw?
- AGreen top (Heparin)
- BRed top (No additive)
- CLight blue top (Sodium Citrate)
- DLavender top (EDTA)
Show answer & explanationAnswer & explanation
Correct answer: A. Green top (Heparin)
According to the CLSI order of draw, green top tubes (containing heparin for chemistry tests like electrolytes) are drawn before lavender top tubes (containing EDTA for hematology tests like CBC). Light blue tops are for coagulation, and red tops are for serum (no additive).
Why the other options are wrong
- B. Red top tubes are for serum collection and are drawn after blood cultures or plain red/gold SSTs, but before green tops.
- C. Light blue top tubes (Sodium Citrate) are typically drawn before green top tubes, but not for a STAT electrolyte panel.
- D. Lavender top tubes (EDTA) are drawn after green top tubes in the CLSI order for routine draws.
CLSI Order of Draw
A standardized sequence for collecting multiple blood tubes during a venipuncture to prevent additive carryover from one tube to another, which could contaminate specimens and alter test results.
- Ensures accurate test results by minimizing additive interference.
- Different additives affect different test types.
- Common sequence: Blood culture, Light blue, Red/Gold SST, Green, Lavender, Gray.
Memory trick: BLGRGL: Blood Cultures, Light Blue, Red/Gold, Green, Lavender, Gray