Clinical evaluation of a microsample coagulation analyzer, and comparison with existing techniques

A new microsample coagulation analyzer (Hemochron Jr.) has recently been developed which performs a modified activated clotting time (ACT+) and an aPTT by using different reagents. The Hemochron Jr. measures the clotting time of a 5-microliter whole-blood sample by an optical detector and extrapolates the results to the activated clotting time (ACT+) or the plasma-activated partial thromboplastin time by using a validated regression analysis. We compared 124 simultaneous ACT+ and Hemochron ACTs, and 53 paired Hemochron Jr. aPTTs and hospital laboratory aPTTs, in 44 patients during coronary intervention. The Hemochron Jr. aPTT closely correlated with the lab aPTT (r = .79, P < .0001), and the test results were available much more rapidly than the lab aPTT (3.5 +/- 1.1 vs. 56.3 +/- 25.5 min, P = 0.0029). A comparison of duplicate ACT+ measurements did not identify a significant difference in the means (292 +/- 115 sec vs. 293 +/- 112 sec, P = 0.72). The ACT+ closely correlated with the Hemochron ACTs (r = .85, P < .0001). At baseline, the mean ACT+ (175 +/- 43 sec) exceeded the Hemochron ACT (144 +/- 36 sec) by 22% (P < .001). After heparin administration, the mean ACT+ (378 +/- 74 sec) exceeded the Hemochron ACT (332 +/- 65) by 12% (P < .001). The Hemochron Jr. provides a fast and reproducible methodology for measuring ACT and aPTT, using a small blood volume. Further studies are required to determine the optimal anticoagulation range when using the Hemochron Jr. during or after interventional procedures.