CPHT Order of Draw & Tube Additives 2

Question 1

What is the correct CLSI-recommended order of draw when collecting multiple tubes via venipuncture?

Accepted Answer

Blood cultures → Citrate → Serum/SST → Heparin → EDTA → Fluoride

Answer

The CLSI-recommended order is blood cultures first, then citrate, serum/SST, heparin, EDTA, and finally fluoride/oxalate tubes to prevent additive carryover between tubes.

Question 2

Why must blood culture bottles be collected before all other tubes in the order of draw?

Accepted Answer

To prevent contamination from tube additives and maintain sterility

Answer

Blood culture bottles are collected first to ensure no tube additive carryover contaminates the sterile culture medium, which could cause false-positive or false-negative microbiology results.

Question 3

Why is the light blue (sodium citrate) tube collected before serum tubes in the standard order of draw?

Accepted Answer

Clot activator from serum tubes could carry over and falsely affect coagulation results

Answer

If serum/SST tubes were collected first, silica clot activator particles could carry over into the citrate tube on the needle and artificially activate coagulation, falsifying PT/INR results.

Question 4

When using a butterfly/winged infusion set, what must be done before collecting a sodium citrate tube?

Accepted Answer

Draw a discard tube to eliminate air from the tubing

Answer

The dead space air in the butterfly tubing must be displaced with blood using a discard tube; otherwise, underfilling disrupts the critical 9:1 blood-to-sodium-citrate ratio needed for coagulation accuracy.

Question 5

In the order of draw, EDTA (lavender) tubes are collected immediately before which tube type?

Accepted Answer

Fluoride/oxalate (gray) tubes

Answer

EDTA tubes are collected before fluoride/oxalate (gray) tubes, as gray tops are always the last tube in the standard CLSI order of draw sequence.

CPHT - Certified Phlebotomist Practice Test

CPHT - Certified Phlebotomist Practice Test

CPHT Order of Draw & Tube Additives 2