Comparative study of two portable systems for oral anticoagulant monitoring

Portable prothrombin time (PT) monitors offer the potential for both simplifying and improving oral anticoagulation management. It is necessary to evaluate their concordance and correlation with other PT systems. Our objective was to evaluate the concordance and clinical correlation of two portable PT determination systems, ProTime (ITC) and CoaguChek S (Roche Diagnostics). In all, 20 healthy individuals and 60 anticoagulated patients stabilized over 3 months in a therapeutic International Normalized Ratio (INR) range between 2-3.5 were studied. A drop of capillary blood was obtained simultaneously from two different fingers of each patient and applied to the monitor's application zone. The mean INR of the patients' blood samples of the two monitors differed by 0.01 units (2.32+/-0.63 for Pro Time and 2.33+/-0.68 for CoaguChek). The percentage of simple concordance and the kappa index were 88.3 and 75.9%, respectively. The coefficient of correlation was 0.922. The mean difference (bias) between the monitors was 0.01. The portable PT monitors evaluated presented a high percentage of concordance in INR results.