Hematology 1 Complete Practice Test 2026

EdTA acts as a strong chelating agent for divalent cations, with calcium binding being its most important effect in stopping clotting. Calcium ions are essential cofactors in multiple steps of the coagulation cascade, helping to assemble coagulation factor complexes on phospholipid surfaces. By tightly binding Ca2+, EDTA removes free calcium from plasma, preventing these calcium-dependent reactions and thus inhibiting clot formation. This is why EDTA is used as an anticoagulant in blood collection tubes. While EDTA can also bind other metals such as magnesium, the clinically relevant action for anticoagulation and many chelation applications is calcium sequestration. It does not directly neutralize thrombin, nor does it specifically bind iron.