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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. Which of the following tubes does NOT require mixing by inversion after collection?

    Answer: Plain red top (no additive, no gel)

    Plain red top tubes contain no additive, so inversion is not needed; the blood simply clots on its own without requiring mixing of any anticoagulant or additive.

  2. What does the additive sodium fluoride in a gray top tube do to blood glucose?

    Answer: Preserves glucose levels by inhibiting glycolysis

    Sodium fluoride inhibits the glycolytic enzyme enolase, halting cellular metabolism and thereby preserving glucose levels for up to 24 hours.

  3. In a point-of-care capillary collection, what is the correct order of fill for microcontainers?

    Answer: Blood gas first, then EDTA, then other additives

    For capillary specimens, CLSI recommends blood gas first, then EDTA tubes, then other additive tubes, and serum or clot tubes last.

  4. A green top tube with lithium heparin is drawn. Which test would be INAPPROPRIATE to run on this sample?

    Answer: Lithium drug level

    Lithium heparin tubes contain lithium, which falsely elevates lithium drug levels; a sodium heparin or serum tube must be used for lithium monitoring.

  5. Which color tube is typically used for erythrocyte sedimentation rate (ESR) testing?

    Answer: Black top (sodium citrate 3.2%)

    Black top tubes containing 3.2% sodium citrate are specifically designated for Westergren ESR testing due to standardized dilution requirements.

  6. What is the consequence of over-inverting an EDTA tube more than the recommended number of times?

    Answer: Platelet clumping and hemolysis may occur, affecting platelet count and CBC results

    Excessive inversion can mechanically damage platelets and red blood cells, causing platelet clumping and hemolysis that invalidate CBC and platelet count results.

  7. A heparin tube (green top) is positioned in the order of draw after the SST. Why is heparin drawn before EDTA but after SST?

    Answer: Heparin carryover into EDTA tubes is less harmful than EDTA carryover into heparin tubes

    Small amounts of heparin carryover into EDTA tubes have minimal clinical impact, whereas EDTA carryover into heparin tubes would chelate calcium and critically disrupt chemistry results.