Calibration of reference thromboplastins and standardisation of the prothrombin time ratio
Kirkwood, T.B.
Thrombosis and Haemostasis 49(3): 238-244
1983
ISSN/ISBN: 0340-6245 PMID: 6879511 Document Number: 200248
Thromboplastins vary in their sensitivity to the hemostatic defect induced by oral anticoagulants. To provide a means of standardizing prothrombin time tests, the WHO adopted in 1977 a scheme for calibrating thromboplastins in terms of an International Reference Preparation. Unfortunately, the model on which this scheme was based does not always hold. A revised calibration model was developed and this was tested in a recent collaborative study. The revised model, which retains fundamentally the same principle for standardizing prothrombin time tests, has proved suitable for calibrating thromboplastins of different species and types, and has certain statistical advantages over its predecessor. In Sept. 1982, the WHO Expert Committee on Biological Standardization adopted the revised model. The nature and rationale of this change and its practical implications are explained.