Which color-coded tube is used for coagulation testing?

Which color-coded tube is used for coagulation testing?

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

Answer: (C)

Coagulation testing relies on a specimen that stays fluid long enough to measure the clotting process, so it uses a tube that prevents clotting while preserving the clotting factors. The light blue top tube contains sodium citrate, an anticoagulant that binds calcium and stops the clotting cascade. This preserves the blood as plasma rather than letting a clot form, which is essential for accurate tests like PT/INR and aPTT. The blood-to-anticoagulant ratio must be exact (about nine parts blood to one part citrate); if the tube isn’t filled properly, the dilution alters results and can give falsely long or short times. After collection, the sample is mixed to distribute the citrate evenly, and calcium is reintroduced during the actual test to allow clot formation in a controlled way for measurement. Other color codes serve different purposes: green tops use heparin for certain chemistry tests and aren’t used for standard coagulation studies; lavender tops use EDTA which inhibits the clotting cascade and would prevent measuring coagulation times; red tops are plain or clot-activator tubes that yield serum rather than plasma. Therefore, for coagulation testing, the light blue tube is the correct choice.

Coagulation testing relies on a specimen that stays fluid long enough to measure the clotting process, so it uses a tube that prevents clotting while preserving the clotting factors. The light blue top tube contains sodium citrate, an anticoagulant that binds calcium and stops the clotting cascade. This preserves the blood as plasma rather than letting a clot form, which is essential for accurate tests like PT/INR and aPTT. The blood-to-anticoagulant ratio must be exact (about nine parts blood to one part citrate); if the tube isn’t filled properly, the dilution alters results and can give falsely long or short times. After collection, the sample is mixed to distribute the citrate evenly, and calcium is reintroduced during the actual test to allow clot formation in a controlled way for measurement.

Other color codes serve different purposes: green tops use heparin for certain chemistry tests and aren’t used for standard coagulation studies; lavender tops use EDTA which inhibits the clotting cascade and would prevent measuring coagulation times; red tops are plain or clot-activator tubes that yield serum rather than plasma. Therefore, for coagulation testing, the light blue tube is the correct choice.