Thrombin clotting time (TCT) is a coagulation assay used to diagnose congenital and acquired fibrinogen deficiency (Adcock et al., Coagulation handbook, Esoterix Coagulation, Austin, TX, 2002), as well as to identify contamination by heparin, prior to performing additional coagulation assays. This test is based on the principle that in citrated plasma, the addition of Thrombin allows for formation of a stable clot. The time required for the formation of a stable clot is recorded in seconds and represents the actual TCT result.