Normotest--thrombotest discrepancy in congenital coagulation disorders of the prothrombin complex and in coumarin-treated patients: a nonspecific phenomenon.

A Normotest (NT)-Thrombotest (TT) discrepancy is claimed to reflect the presence of coumarin-induced inhibitors or intravascular coagulation, or both. The results of this study indicate, however, that a significant NT-TT discrepancy is also present in all plasmas from patients who have congenital coagulation disorders of the prothrombin complex. None of these patients had received an anticoagulant or showed any sign of intravascular clotting; nevertheless the discrepancy observed was similar to that found in plasmas of coumarin-treated patients: average values were 0.437 and 0.450, respectively. As no inhibitor was present in the congenital coagulation disorders, except in hemophilia BM, the phenomenon does not appear to be specific for coumarin plasma. This indicates that the NT/TT discrepancy is a non-specific phenomenon that does not seem to provide any additional information about coumarin-treated patients compared with that obtainable by means of a simple prothrombin time test.