Anticoagulants in Blood Collection: Mechanisms of Common Additives

Anticoagulants prevent blood clotting in collection tubes by targeting different steps of the coagulation cascade:

• EDTA (Ethylenediaminetetraacetic acid): Chelates calcium ions (Ca²⁺), essential for clotting factor activation, preventing prothrombin conversion to thrombin.
• Sodium Citrate: Forms a reversible calcium-chelate complex, inhibiting coagulation. Used for coagulation studies (PT/INR, aPTT).
• Heparin: Enhances antithrombin III activity, inhibiting thrombin and factor Xa, thus preventing fibrinogen-to-fibrin conversion.
• Oxalate: Precipitates calcium ions as calcium oxalate, removing them from the clotting cascade.
• Sodium Fluoride: Inhibits glycolysis (glycolytic enzyme inhibitor), preserving glucose levels; also has antibacterial properties.

Selection depends on the intended laboratory test.