Phlebotomy and Lab Procedures Flashcards

Which additive in a lavender-top tube prevents clotting by binding calcium?

Answer: EDTA

EDTA (ethylenediaminetetraacetic acid) chelates calcium ions to prevent coagulation in lavender-top tubes.

A patient's arm shows a hematoma forming during venipuncture. What is the FIRST action?

Answer: Release the tourniquet and remove the needle

When a hematoma forms, the phlebotomist must immediately release the tourniquet and remove the needle to stop blood from leaking into surrounding tissue.

Which vein is considered the FIRST choice for routine venipuncture in adults?

Answer: Median cubital vein

The median cubital vein is preferred because it is large, well-anchored, and usually close to the surface with minimal nerves nearby.

What is the purpose of the 'order of draw' in phlebotomy?

Answer: To prevent cross-contamination of additives between tubes

The order of draw minimizes carryover of tube additives into subsequent tubes, which could interfere with test results.

A gray-top tube contains sodium fluoride. What is its PRIMARY purpose?

Answer: Inhibit glycolysis to preserve glucose levels

Sodium fluoride inhibits glycolytic enzymes, preventing red blood cells from consuming glucose and ensuring accurate glucose measurements.

Which condition results from excessive tourniquet pressure or prolonged application?

Answer: Hemoconcentration

Prolonged tourniquet application causes fluid to shift out of vessels, concentrating cellular components and analytes — a condition called hemoconcentration.

In the context of chain of custody, which specimen type typically requires this strict documentation?

Answer: Drug-of-abuse urine specimen

Drug-of-abuse specimens require chain of custody documentation to ensure specimen integrity and legal defensibility of results.