[Some aspects of newly developed instruments for blood coagulation tests]

Five newly developed instruments for five routine blood coagulation tests including prothrombin time, APTT, thrombotest, normotest and fibrinogen assay and the other specialized tests were introduced by each manufacturer. In four instruments, the principal of clot detection is based on the change of optical density due to fibrin thread. One instrument detects viscosity change. All instruments were easy to use due to full-automation, and the precision and accuracy in one laboratory use were high in quality. There were difficult problems when a user switches from the reagent recommended by the manufacturer to another commercially available one. The user needs to re-evaluate the standard curve using international reference plasma. In Japan, international normalized ratio (INR) presentation of prothrombin time is not common even in a large scale laboratory. When a patient with warfarin moves to another hospital, the presentation of prothrombin time from the former laboratory can not be used because of the difference in reagent and equipment. Much confusion concerning prothrombin time occurred due to differences in reagent and equipment after the Hanshin-Awaji earthquake. Many patients taking warfarin had to evacuate under severe stress condition, and had prothrombin time out of the optimal therapeutic range not knowing whether it was due to quake-stress or intra-laboratory difference. Selection of automated coagulation instrument which can easily print out the INR in prothrombin time is recommended.