Statistical Correlation and Heparin Sensitivity of Activated Partial Thromboplastin Time, Whole Blood Coagulation Time, and an Automated Coagulation Time

Abstract

In vitro heparinization experiments were done to determine the heparin sensitivity and statistical correlation of the three coagulation tests in order to see whether automated whole blood coagulation time (ACT) and activated partial thromboplastin time (APTT) could be substituted for whole blood coagulation time (WBCT). WBCT and ACT were linearly related to each other and to blood heparin level. Log APTT gave a linear correlation with blood heparin level and with the two whole blood coagulation tests. Two to 2½ times baseline WBCT corresponded to an APTT of 2.7 to 4.2 times baseline (average 90 to 150 sec), and to an ACT of 1.6 to 2.2 times baseline (average 410 to 570 sec). All three tests were sensitive enough to heparin effect for use in monitoring of patients. Any attempt to substitute APTT for WBCT must take into consideration the nonlinear relationship between APTT and WBCT.