Performance of a point-of-care device in determining prothrombin time in an anticoagulation clinic

New portable devices for the measurement of the prothrombin time and the international normalized ratio (INR) from capillary blood samples have demonstrated to have good correlation with classic laboratory methods in multiple clinical settings. In this study, we evaluated the performance of the point-of-care device CoaguChek XS (CoaguChek XS; Roche Diagnostics, Basel, Switzerland), comparing the INR results with the standard laboratory method (automatic coagulometer) in an outpatient anticoagulation clinic. Results were compared by linear regression and Bland-Altman plot. Two hundred paired results were collected from 170 patients in a period of 90 days. The main indications for anticoagulation were prophylaxis of venous thromboembolic events, atrial fibrillation and prosthetic heart valves. Mean INR results obtained with the portable device and with the standard laboratory method were 2.22 ± 0.70 and 2.30 ± 0.77, respectively. The proportion of patients with supratherapeutic INRs was 13.5%. The CoaguChek XS monitor tended to underestimate the INR on average by 0.08 U. The correlation coefficient (R) between the two methods was 0.91 (P < 0.0001). The CoaguChek XS device is suitable for INR monitoring in patients in outpatient oral anticoagulation clinics.