Dosage and control of oral anticoagulants: an international collaborative survey

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Abstract
An international survey of oral anticoagulant dosage compared the mean dosage prescribed in hospitals in 23 countries. Participants using the Quick prothrombin time test were asked to assess the adequacy of dosage of a lyophilized test plasma which was midtherapeutic by using the British Comparative Thromboplastin (BCT). The overall mean dosage was similar for the groups of laboratories when using the Quick test and human brain thromboplastin and Thrombotest although wide differences existed between individual centers. These discrepancies were due partly to the adoption of different intensities of anticoagulation. Local differences in patients'' response to anticoagulants were apparent; North American centers prescribed a higher mean dose with a more intense therapeutic range than did Europeans. Hong Kong physicians prescribed a much lower dose than the rest of the world, although the intensity of their treatment was comparable; South African hospitals give moderate doses of warfarin despite a conservative therapeutic range. Such geographical variation in response invalidates standardization of anticoagulant treatment based on the mean dosage approach.