Level of agreement between laboratory and point-of-care prothrombin time before and after cardiopulmonary bypass in cardiac surgery

BackgroundHemostasis monitoring in cardiac surgery could benefit from an easy to use and fast point-of-care coagulation monitor, since routine laboratory tests have a delay of 30-45 minutes. This study investigated the level of agreement between the point-of-care prothrombin time (PT) with central laboratory PT before and after cardiopulmonary bypass.MethodsBland Altman and error grid analysis were used to analyze the agreement between the point-of-care Coaguchek XS Pro device (POC-PT) and the central laboratory prothrombin time (LAB-PT) before cardiopulmonary bypass (CPB) and 3 minutes after protamine administration. Prothrombin times were expressed in international normalized ratios (INR).ResultsThe average POC-PT and LAB-PT values of 73 patients were 1.06 ± 0.14 and 1.09 ± 0.13 (P = 0.10) before CPB. POC-PT measurements before CPB showed a good agreement with the LAB-PT, with a bias of − 0.02 ± 0.07 INR and 94% of the values being represented in the clinical acceptable zone of error grid analysis. The mean POC-PT 3 minutes after protamine administration was significantly lower than the LAB-PT (1.35 ± 0.12 vs. 1.70 ± 0.18; P < 0.001). The PT at 3 minutes after protamine administration showed a bias of 0.36 ± 0.14, and 82% of the values were located outside of the clinical acceptable zone in the error grid analysis.ConclusionsPoint-of-care prothrombin time testing was in concordance with conventional laboratory PT prior to cardiopulmonary bypass. At 3 minutes following protamine administration, PT values of the point-of-care device were structurally lower than the laboratory PT values, leading to a disagreement between both tests at that time point.