Prospective double-blind clinical trial of bovine, human, and rabbit thromboplastins in monitoring long-term oral anticoagulation.

A prospective double-blind trial was performed to investigate the safety of long-term oral anticoagulant control when dosaged adjustment depends on the prothrombin times assessed with one type of thromboplastin being calculated as if assayed by another type. The three main types of thromboplastin, i.e., bovine (Thrombotest), human (British Comparative Thromboplastin), and rabbit (Simplastin Automated) were tested. Before entering the actual trial, patients had been checked with the bovine type of thromboplastin. During the actual comparison study, prothrombin times obtained with the human and the rabbit types of thromboplastin were translated, using the appropriate calibration data, into terms of the bovine type of thromboplastin, which were used for dosage prescription. After six months, all patients returned to bovine-type thromboplastin control. No substantial difference among the three groups was observed in the prothrombin times, the dosage of the anticoagulant, the bleeding complications, and the dropouts. It was concluded that the safety of monitoring patients receiving long-term oral anticoagulation was independent of the type of thromboplastin used.