What method used to prevent blood in the antigoaculant tubes from clotting?

Anticoagulant tubes typically contain substances such as EDTA, sodium citrate, or lithium heparin, which prevent blood from clotting by inhibiting the coagulation cascade. EDTA binds calcium ions, which are essential for blood coagulation, while sodium citrate works by chelating calcium, and lithium heparin activates antithrombin, a protein that inhibits thrombin and factor Xa. These anticoagulants allow for the preservation of blood samples for various laboratory analyses without clot formation.