Order of Draw and Additives Flashcards

Which tube is collected FIRST in the venipuncture order of draw?

Answer: Blood culture bottles

Blood culture bottles are always collected first to minimize contamination risk from skin flora.

What additive is found in a royal blue top tube used for trace element testing?

Answer: EDTA or no additive (K2EDTA or plain)

Royal blue tubes contain either EDTA or no additive and are made with trace-element-free stoppers to prevent contamination.

A gray top tube contains which combination of additives?

Answer: Sodium fluoride and potassium oxalate

Gray top tubes contain sodium fluoride (a glycolytic inhibitor) and potassium oxalate (an anticoagulant) for glucose testing.

In the order of draw, where does the EDTA (lavender) tube fall relative to heparin tubes?

Answer: After heparin tubes

EDTA tubes are drawn after heparin (green) tubes to prevent EDTA carryover from affecting coagulation or chemistry tests.

Which tube additive works by binding calcium ions to prevent coagulation?

Answer: EDTA

EDTA chelates (binds) calcium ions, which are essential for the coagulation cascade, thereby preventing clotting.

A phlebotomist draws a light blue top tube and notices the tube did not fill completely. What is the main concern?

Answer: The blood-to-additive ratio will be incorrect, affecting PT/INR results

Light blue (sodium citrate) tubes require a precise 9:1 blood-to-anticoagulant ratio; underfilling alters this ratio and skews coagulation test results.

Which color tube would be used when a physician orders a stat potassium level and the lab uses heparin plasma?

Answer: Green (lithium heparin)

Green top tubes with lithium heparin are used for plasma chemistry tests like potassium, providing faster results than serum tubes since no clotting is needed.