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Order of Draw & Tube Additives Flashcards

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  1. How many times should a lavender (EDTA) tube be gently inverted immediately after blood collection?

    Answer: 8-10 inversions

    EDTA tubes require 8-10 gentle inversions to ensure complete mixing of blood with the anticoagulant, preventing microclot formation that would invalidate a CBC or differential.

  2. A sodium citrate tube must be filled to what level for coagulation results to be considered valid?

    Answer: Within ±10% of the required fill volume

    Citrate tubes must be filled to within ±10% of their required volume to maintain the critical 9:1 blood-to-sodium-citrate ratio needed for accurate PT/INR and aPTT results.

  3. If EDTA carryover from a lavender tube occurs into a serum chemistry tube, which electrolyte result is most likely to be falsely elevated?

    Answer: Potassium (K+)

    Dipotassium EDTA carryover into chemistry tubes can cause falsely elevated potassium levels, potentially triggering unnecessary clinical interventions for pseudo-hyperkalemia.

  4. A phlebotomist accidentally draws an SST (gold) tube before the light blue (citrate) tube. What is the correct corrective action?

    Answer: Draw a discard tube to flush residual clot activator before collecting the citrate tube

    Drawing a discard tube after the SST flushes clot activator particles from the needle, preventing them from entering the citrate tube and falsely shortening coagulation clotting times.

  5. For which analyte is a plain red top tube (no gel separator) preferred over a gold SST tube?

    Answer: Serum iron testing

    Plain red top tubes are preferred for serum iron testing because the polyester gel in SST tubes can adsorb iron, leading to falsely decreased serum iron concentration results.

  6. How many inversions are recommended for a gold SST tube immediately after blood collection?

    Answer: 5-6 inversions

    Gold SST tubes should be inverted 5-6 times to mix the clot activator with blood; fewer inversions may cause incomplete clotting, while excessive inversion may cause hemolysis.

  7. How does sodium fluoride in a gray top tube preserve glucose levels in a blood specimen?

    Answer: It inhibits the glycolytic enzyme enolase, stopping glucose consumption by red blood cells

    Sodium fluoride inhibits enolase, a key glycolytic enzyme, preventing red blood cells from continuing to metabolize glucose after collection and preserving accurate glucose levels for up to 24 hours.