Background: Warfarin reduces the risk of stroke in patients with atrial fibrillation, but requires a moderate-to-high time in therapeutic range (TTR). We hypothesized that point-of-care (POC) testing for prothrombin time-internationalized normalized ratio (PT-INR) could improve the TTR in patients receiving warfarin.
Methods and results: Eight outpatient clinics that introduced POC testing for PT-INR participated in this study. We identified 148 consecutive patients who received warfarin for at least 12 months before and after the introduction of POC testing. We compared the TTR before and after the introduction of POC testing for each patient. TTR after the introduction of POC testing was significantly higher than that beforehand (51.9%±33.0% vs. 69.3%±26.3%; P<0.0001). The improvement in TTR was statistically significant in patients who had low TTR (<70%) before the introduction of POC testing. After the introduction of POC, the time spent above the target INR showed no significant change (3.7%±10.6% vs. 3.3%±6.3%, P=0.7322), while that spent below the target INR improved significantly (44.4%±34.4% vs. 27.4%±27.6%, P<0.0001).
Conclusions: The introduction of POC testing was associated with an improvement in TTR, mainly through a reduction in the time spent below the target INR.