Comparison of Point-of-Care Activated Clotting Time Methods in Different Clinical Settings in a Large Academic Medical Center

Abstract

Objectives: This study is a comparative analysis of measured activated clotting time (ACT) values by use of 5 different point-of-care (POC) ACT methods spanning the range detected during different clinical procedures at our institution. Methods:We determined the correlation, imprecision, and differences in measured ACT values with use of 4 POC ACT methods compared with a reference ACT method in 41 venous whole blood samples collected from 25 adult patients undergoing interventional procedures. The POC ACT methods evaluated included the i-STAT with kaolin activator in prewarm mode, i-STAT with Celite activator in prewarm and nonprewarm modes, ACTPlus, and HMSPlus, which was designated the reference method. Each venous whole blood patient sample was tested in duplicate on each POC ACT test system (total n = 410 ACT measurements). Analyses of imprecision and differences in measured ACT values were stratified by moderate (100 -299 s) and high (≥300 s) ACT ranges. Results:In this study population, measured ACT values ranged from 100 -835 s with use of the HMSPlus. All methods demonstrated good correlation (r ≥ 0.95) in ACT values compared to the reference method. Imprecision varied by method with ranges of 1.7%-2.7% CV in the moderate ACT range and 2.5%-4.8% CV in the high ACT range. ACTPlus and i-STAT-Celite-prewarm methods exhibited proportional differences in measured ACT values whereas the i-STAT-Celite-nonprewarm and i-STAT-kaolin-prewarm demonstrated constant differences in measured ACT values compared to HMSPlus. Conclusions:ACT values correlate well between POC methods. Imprecision and difference profiles vary by method; notably, imprecision exceeds systematic differences in the high ACT range and contributes to intermethod differences that are limitations worthy of consideration when contemplating a change in ACT methods. IMPACT STATEMENTMeasurement of ACT is particularly useful during interventional clinical procedures involving use of heparin therapy to facilitate rapid decision-making for management of patient hemostasis. The present study findings demonstrate differences in measured ACT values between 5 different POC ACT methods and the effect analytical variables have on ACT test performance. Education of health-care professionals is needed regarding differences in measured ACT values if changing or interchanging ACT test systems.

Laboratory Assessment of Unfractionated Heparin (UFH) with Activated Clotting Time (ACT) and Anti-Xa Activity during Peripheral Arterial Angiographic Procedure

“…However, in different hospitals, localized protocols are often in use, as evidenced by the varying ACT targets even in cardiopulmonary bypass, with the longest experience with the assay [ 10 ]. While different ACT coagulometers generally provide similar results, different ACT devices have varying sensitivities to UFH as well as coagulation factor levels and other patient-related factors, supporting the use of localized ACT target ranges [ 11 ]. There is no reference material or gold standard for ACT testing.…”