Phlebotomy Plan

CPT practice question: Routine Blood Collections

Routine Blood CollectionsDifficulty 4/5

A lavender EDTA tube is mistakenly drawn before the light blue citrate tube. What is the principal concern?

  1. ACitrate carryover binds calcium and distorts the haematology result
  2. BEDTA carryover activates clotting and shortens the coagulation result
  3. CNeither result is affected, provided both tubes are inverted correctly
  4. DEDTA carryover binds calcium and distorts the coagulation result
Show answer and rationale

Correct: D. Both EDTA and citrate work by removing calcium, so EDTA carried into a citrate tube adds an uncontrolled anticoagulant to a test that depends on a precise citrate-to-blood ratio.

  • A — The contamination travels forward from the tube drawn first, so it is EDTA reaching citrate.
  • B — EDTA is an anticoagulant; it prevents clotting rather than activating it.
  • C — Inversion mixes the additive already present; it cannot remove contamination from another tube.

Concept being tested

28 of the 100 scored items and the second largest domain. Equipment selection and verification, needle gauges and lengths, adapting technique for patients with burns, dementia or bleeding disorders, tourniquet application and removal, site selection by observation and palpation, antisepsis, anchoring the vein, needle insertion angle, following the order of draw for both venipuncture and capillary collection, recognising and responding to complications such as syncope, hematoma, petechiae and nerve pain, needle safety devices, tube inversion, dermal puncture, post-procedural care and labelling. — 28% of the exam. Study guide for Routine Blood Collections.

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Primary references

  1. Order of Blood Draw Tubes and Additives — Clinical and Laboratory Standards Institute (CLSI) · primary · retrieved 2026-09-22, verified 2026-09-22
  2. WHO Guidelines on Drawing Blood: Best Practices in Phlebotomy — World Health Organization · government · retrieved 2026-09-22, verified 2026-09-22
Last reviewed: 2026-10-07Reviewed by: Maria Torres, CPT, RMA (AMT), Clinical laboratory educator & venipuncture safety reviewHow we verify facts