Original Article

Activated Clotting Time (ACT): The Reproducibility of Three Techniques

he Cleveland Clinic Foundation, Cleveland, OH

^* Direct communications to: Paul V. Sillick, Department of Perfusion Services, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44106

Abstract

(J. Extra-Corpor. Technol. 19[3] p. 265-267 Fall 1987, 6 ref.) The ACT has routinely been used to monitor anticoagulation during surgical procedures, including open heart surgery. Since there is no laboratory substrate that can serve as a control for the test, it is important to know the reproducibility of the ACT. This study examined the reproducibility of three ACT techniques using the single syringe method.

Before heparinization, a 7cc sample of blood was collected from each of 50 open heart surgery patients. From this sample two Hemochron ACTs (H-ACT), two Sonoclot Coagulation ACTs (SonACT), and two manual ACTs (M-ACT) were simultaneously performed. The mean ± S.D. (seconds) was found to be 105.6 ± 31.8 for the SonACT, 109.7 ± 27.2 for the H-ACT, and 126.8 ± 15.4 for theM-ACT. Five minutes after heparinization the ACTs showed means of 485.5 ± 93.3 for the Son ACT, 455.6 ± 1 01.9 for the HACT, and 471.2 ± 84.9 for the M-ACT.

The absolute value of the difference between the paired observations, a function of the reproducibility, was seen to have a mean of 8.8 ± 13.4 for the SonACT, 6.1 ± 7.0 for the H-ACT, and 8.3 ± 7.6 for theM-ACT. Post heparinization, the absolute difference between the paired observations gave means of 90.7 ± 99.7 for the SonACT, 56.7 ± 59.8 for the HACT, and 40.4 ± 45.4 for the M-ACT.

Before heparinization, all three techniques gave acceptable results. With heparinization the M-ACT showed the most reproducibility, followed by the H-ACT, while the SonACT provided the least consistent results.