Which color tube top is associated with citrate anticoagulant for coagulation testing?

• A. Red
• B. Gold
• C. Lavender
• D. Light Blue

Answer: (D)

The main idea here is that tube color signals what additive is inside, and for coagulation testing you need an anticoagulant that preserves clotting factors. Light blue tops contain sodium citrate, which is specifically used as the anticoagulant for coagulation tests.

Sodium citrate works by temporarily binding calcium, stopping the blood from clotting. This lets you measure clotting times like PT and aPTT on plasma rather than serum. The accuracy depends on the correct blood-to-anticoagulant ratio (about 9:1) and proper mixing. That’s why these tubes must be filled to the indicated line and gently inverted several times to mix.

Other tube colors serve different purposes: red tops are without anticoagulant (used for serum), gold tops contain a clot activator with a gel for serum, and lavender tops contain EDTA (used for complete blood counts) and are not suitable for routine coagulation studies because EDTA interferes with clotting factors.