The Activated Partial Thromboplastin Time in the Control of Heparin Treatment

Summary The effect of heparin on the activated partial thromboplastin time and whole blood clotting time was measured in 30 patients with thrombo‐embolic disease. In 27 of these patients there was good correlation between the results of the two tests. Three patients showed little change of the activated partial thromboplastin time, although the clotting time was prolonged by heparin. It is uncertain at present which of these two tests provides the better measure of the antithrombotic effects of heparin when such a discrepancy exists. However, the activated partial thromboplastin time is more convenient to perform and we consider it to be the more suitable test for the routine control of heparin therapy.