Point-of-care (POC) versus central laboratory instrumentation for monitoring oral anticoagulation

Point-of-care (POC) instruments employing fingerstick whole blood to monitor patients treated with warfarin are a popular alternative to complex, central laboratory coagulation analyzers utilizing citrated plasma derived from venipuncture. We investigated the accuracy of two widely utilized POC instruments for oral anticoagulation monitoring compared with a central laboratory instrument. Instrument-to-instrument variation differed for the two POC instruments, which correlated with the central laboratory instrument, but exhibited positive bias of 0.24-0.35 INR units. Positive bias increased as the INR values increased. We conclude that clinicians should exercise caution when interpreting results generated by POC monitors, particularly at high INR values. A high POC measurement of INR does not necessarily warrant decreasing the warfarin dose. Instead, a predefined cut-off range for high INR values generated by POC instruments should mandate confirmatory testing with central laboratory instrumentation.