For coagulation testing, which anticoagulant is preferred to minimize preanalytical artifacts?

• A. Sodium Citrate
• B. EDTA
• C. Heparin
• D. ACD

Answer: (A)

Focusing on preventing artificial changes during sample collection, you want an anticoagulant that stops clotting without permanently removing calcium, so the test can accurately start coagulation in the lab. Sodium citrate does this by reversibly binding calcium in the blood. This keeps the sample fluid and stable while preventing in vitro clotting, and then calcium can be reintroduced during the assay to measure clotting times like PT and aPTT reliably. The standard mix—blood drawn with a 3.2% sodium citrate solution in a 9:1 ratio—ensures a consistent plasma citrate level and minimizes variable artifacts.

Other anticoagulants either bind calcium too tightly and aren’t reversible for testing, interfere with coagulation assays, or aren’t suitable for routine PT/aPTT measurements. For example, EDTA is great for hematology but distorts coagulation tests; heparin can alter clot-based results; ACD is used mainly for specialized applications. That’s why sodium citrate is preferred to minimize preanalytical artifacts in coagulation testing.