Which tube is used for coagulation testing such as PT, PTT, and PFA?

Which tube is used for coagulation testing such as PT, PTT, and PFA?

• A. Green Tube — Heparin
• B. Red Tube — No additive
• C. Lt Blue Tube — Na Citrate
• D. Gray Tube — Na Fluoride/K Oxalate

Answer: (C)

Coagulation tests like PT, aPTT, and PFA rely on plasma prepared with an anticoagulant that preserves clotting factors by temporarily binding calcium. The light blue top tube contains sodium citrate, which acts as a reversible calcium chelator. When blood is collected in this tube and mixed gently, it remains fluid and the clotting factors stay intact for accurate testing. Before testing, the calcium is reintroduced, allowing the clotting times to be measured correctly. This tube is specifically designed for coagulation work and yields reliable results. The other tubes aren’t suitable for this purpose: a green-top tube uses heparin, which can alter clotting times and interfere with certain coag tests; a red-top tube has no additive and yields serum after the blood clots, not the plasma needed for these tests; and a gray-top tube contains fluoride and potassium oxalate, used mainly for glucose testing and also has calcium-chelating effects, which disrupt coagulation measurements.

Coagulation tests like PT, aPTT, and PFA rely on plasma prepared with an anticoagulant that preserves clotting factors by temporarily binding calcium. The light blue top tube contains sodium citrate, which acts as a reversible calcium chelator. When blood is collected in this tube and mixed gently, it remains fluid and the clotting factors stay intact for accurate testing. Before testing, the calcium is reintroduced, allowing the clotting times to be measured correctly. This tube is specifically designed for coagulation work and yields reliable results.

The other tubes aren’t suitable for this purpose: a green-top tube uses heparin, which can alter clotting times and interfere with certain coag tests; a red-top tube has no additive and yields serum after the blood clots, not the plasma needed for these tests; and a gray-top tube contains fluoride and potassium oxalate, used mainly for glucose testing and also has calcium-chelating effects, which disrupt coagulation measurements.