Phlebotomy Test Order of Draw and Additives 3

Question 1

Why is the serum separator tube (SST) drawn AFTER the light blue coagulation tube?

Accepted Answer

SST contains clot activators that could contaminate the citrate tube

Answer

SST tubes contain silica clot activators that would contaminate the sodium citrate coagulation tube if drawn first, falsely activating clotting.

Question 2

What is the purpose of the gel separator in an SST or PST tube?

Accepted Answer

It forms a barrier between serum/plasma and cells after centrifugation

Answer

The thixotropic gel migrates during centrifugation to form a stable barrier between the cellular portion and the serum or plasma.

Question 3

Which tube is used for a complete blood count (CBC)?

Accepted Answer

Lavender (EDTA)

Answer

Lavender top tubes containing EDTA are the standard for CBCs because EDTA preserves cell morphology and prevents platelet clumping.

Question 4

A phlebotomist is drawing multiple tubes and needs a sodium citrate tube. What should be done if no discard tube is available when using a butterfly needle?

Accepted Answer

Use the first tube drawn as a discard tube to purge air from the tubing

Answer

When using a butterfly needle, the tubing dead space fills with air before blood — drawing a discard tube first ensures the sodium citrate tube fills to the correct volume.

Question 5

Which anticoagulant is used in yellow-topped ACD (acid citrate dextrose) tubes and what are they primarily used for?

Accepted Answer

Acid citrate dextrose — used for blood bank and paternity testing

Answer

ACD tubes contain acid citrate dextrose, which preserves red blood cell viability, making them ideal for blood bank, DNA, and paternity studies.

Phlebotomy Practice Test

Phlebotomy Practice Test

Phlebotomy Test Order of Draw and Additives 3