In vitro comparative study of activated clotting time in fresh human whole blood with various levels of coagulability using two devices

With increasing demand for a variety of clinical diagnostics related to blood coagulability such as activated clotting time (ACT), several measurement devices have been developed. Recently, a new ACT measurement device, the Coagulometer CA-200, has become available. One issue is that there will inevitably be differences in measured ACT values among different devices. In addition, as ACT measure ment becomes more widely used in clinical practice, measurement of blood coagulation will be required in patients with a wider range of blood coagulability. Consequently, the purpose of this study was to investigate blood coagulability as the function of protamine dose in heparin sodium-treated fresh human blood and to examine the correlation between measured ACT values from two devices, namely, the Coagulometer CA-200 and Hemochron Jr. Signature+. The results showed similar ACT curves as the dose of protamine was increased, becoming asymptotic at higher coagulability conditions. Under the theoretical maximal procoagulant condition, ACT values were 108 ± 22.5 and 122 ± 11 s for the CA-200 and Hemochron devices, respec-tively. In blood with the maximum heparin sodium content of 7 U/mL, the measured ACT was 800 and 600 s for the respective devices. Furthermore, there was a linear relationship between the ACT measurements of the two devices. This study clearly showed the feasibility of measurement with the CA-200 and its relatively higher resolution in low coagulability conditions.