Question 1
A provider orders a PT/INR, a comprehensive metabolic panel in a gold gel tube and a CBC. Which sequence is correct with evacuated tubes?
Order of draw drill
Put the tubes in the order they are filled. Each round deals a new set of tubes; you get the reason for every one, so the order sticks. It follows the CLSI order of draw used on both exams.
| Evacuated tubes | Cultures, light blue, red or gold, green, lavender, gray |
|---|---|
| Capillary (skin puncture) | Blood gases, EDTA, other additive tubes, serum last |
| Butterfly, light blue first | A discard tube first, to fill the tubing's air space |
Put the tubes in order
Collection
Choose the tubes in the order they are filled. Choose a placed tube again to take it back.
Why the order matters
The needle passes through every stopper. A little additive from one tube can ride into the next and change its result: EDTA carried into a serum tube raises potassium and lowers calcium, and clot activator carried into a light blue tube upsets clotting times.
So the sterile cultures go first, the clotting tube comes before anything that starts or blocks clotting, and the strongest additives, EDTA and fluoride, go last.
The order in full
- Blood cultures (or a yellow SPS tube)
- Light blue: sodium citrate, for coagulation tests
- Red or gold: serum tubes, with or without gel
- Green: heparin, with or without gel
- Lavender or pink: EDTA
- Gray: sodium fluoride and potassium oxalate
Capillary order is different
On a finger or heel stick, the EDTA tube is filled early because platelets clump at the puncture site, and serum tubes go last.
Try 3 questions
Question 2
A lavender tube is drawn by mistake before a gold tube for electrolytes, and EDTA carries over. Which result change is expected?
Question 3
A finger stick must fill an EDTA microtube for a CBC and a serum microtube. Which is filled first?
Next step
Questions people ask
What is the order of draw in phlebotomy?
Blood cultures, then light blue (citrate), then red or gold serum tubes, then green (heparin), then lavender (EDTA), then gray (fluoride).
Why does the light blue tube come before the serum tube?
Clot activator from a serum tube could carry into the citrate tube and change coagulation results.
When do I need a discard tube?
When a butterfly set is used and a light blue tube is the first tube, because the tubing's air would leave the tube underfilled.