Introduction of international normalized ratio of prothrombin time to evaluate multiple depletions of coagulation factors

Prothrombin time(PT) is utilized in worldwide as a global coagulation test reflected multiple depletions of coagulation factors in diseases such as severe liver dysfunction and Disseminated Intravascular Coagulation(DIC). However, standardization of regents and result reporting methods are not established yet except International Normalized Ration(INR) for control of oral anticoagulant therapy(OAT). We evaluated whether INR is capable for defect of multiple coagulation factors except OAT, using absorbed plasma and different origins of thromboplastin; human recombinant, human placenta, cultured human cell and rabbit brain. PTs of individual 90 samples(group MC) absorbed with BaSO4 and/or bentnite and 60 samples(group W) from patients with OAT were measured with 20 normal plasmas with respective reagents. Sensitivities of four reagents to plasma of group W and MC were determined respectively against human recombinant thromboplastin(ISI = 1.03). Both of human thromboplastin showed that sensitivity to absorbed plasma was very close to OAT plasma, whereas reductions of sensitivity to 84% and 66% for absorbed plasma were revealed in both of rabbit thromboplastins. Correlations of INRs calculated by two different sensitivities, one is to absorbed plasma and another to OAT plasma, indicated that discrepancy of sensitivities was emphasized as large slopes(1.50 and 2.76) of regression lines and large intercepts in rabbit thromboplastins, although slopes closed to 1.0 with small intercepts in both of human thromboplastins. We concluded that use of human thromboplastin was the first priority to introduce INR system for evaluation of multiple coagulation factors depletions.