Comparison of thromboplastins used for oral anticoagulant control.

Prothrombin ratio (PR) ranges of 1.5-2.5 based on clinical effect are used for oral anticoagulant control with most commercially available thromboplastins, whereas with Australasian Reference Thromboplastin (ART) 2.0-3.5 is recommended. Plasmas from patients taking oral anticoagulants were concurrently tested with various thromboplastins and interrelationships between these products were determined. Although PR's with ART appear higher, in fact therapy based on ART guidelines is considerably more conservative than that monitored with most commercial thromboplastins.