What additive is found in the light-blue top tube?

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Multiple Choice

What additive is found in the light-blue top tube?

Coagulation testing relies on an anticoagulant that preserves clotting factors without destroying them. The light-blue top tube contains sodium citrate, which binds calcium in the blood. This temporary removal of calcium stops coagulation so the plasma can be analyzed for tests like PT and aPTT. Because the citrate binding is reversible, calcium can be restored in the lab assay, allowing clotting to occur under controlled conditions and yielding accurate results. The tube is designed to be filled to a specific 9:1 blood-to-additive ratio; if it’s under- or overfilled, the ratio changes and coagulation times can be falsely prolonged or shortened. EDTA is used for CBCs, heparin for chemistry tests, and oxalate (often with fluoride) for glucose testing, so those options don’t fit the light-blue tube’s purpose.

Coagulation testing relies on an anticoagulant that preserves clotting factors without destroying them. The light-blue top tube contains sodium citrate, which binds calcium in the blood. This temporary removal of calcium stops coagulation so the plasma can be analyzed for tests like PT and aPTT. Because the citrate binding is reversible, calcium can be restored in the lab assay, allowing clotting to occur under controlled conditions and yielding accurate results. The tube is designed to be filled to a specific 9:1 blood-to-additive ratio; if it’s under- or overfilled, the ratio changes and coagulation times can be falsely prolonged or shortened. EDTA is used for CBCs, heparin for chemistry tests, and oxalate (often with fluoride) for glucose testing, so those options don’t fit the light-blue tube’s purpose.

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