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Order of Draw and Additives Flashcards

7 cards from real Phlebotomy Test practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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

    Answer: SST contains clot activators that could contaminate the citrate tube

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

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

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

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

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

    Answer: Lavender (EDTA)

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

  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?

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

    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.

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

    Answer: Acid citrate dextrose — used for blood bank and paternity testing

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

  6. How many times should a sodium citrate (light blue) tube be inverted after collection?

    Answer: 5–6 times

    Light blue tubes should be inverted 3–4 times according to most manufacturers; however, CLSI and many references cite 3–4 gentle inversions to mix the anticoagulant without activating platelets.

  7. Which statement about the gold or tiger-striped SST tube is correct?

    Answer: It contains a clot activator and gel separator for serum chemistry testing

    Gold or tiger-striped SST tubes contain silica particles to activate clotting and a gel separator, and are used for serum-based chemistry tests after centrifugation.