Objective: Warfarin therapy has some difficulties in terms of close monitoring and dosage. This study aims to evaluate the effect of same-fixed versus different-variable physician-based monitoring of warfarin therapy on treatment quality and clinical end-points.
Methods: A total of 625 consecutive patients requiring warfarin treatment were enrolled at seven centers. INR values of the patients measured at each visit and registered to hospital database were recorded. Time in therapeutic range (TTR) was calculated using linear interpolation method (Rosendaal's method). A TTR value of ≥65% was considered as effective warfarin treatment. If a patient was evaluated by the same-fixed physician at each INR visit, was categorized into the same-physician (SP) group. In contrast, if a patient was evaluated by different-variable physicians at each INR visit, was categorized into variable physician (VP) group. Enrolled patients were followed up for bleeding and embolic events.
Results: One hundred and fifty-six patients (24.9%) were followed by SP group, 469 (75.1%) patients were followed by VP group. Median TTR value of the VP group was lower than that of SP group (56.2% vs. 65.1%, respectively, p=0.009). During median 25.5 months (9-36) of follow-up, minor bleeding, major bleeding and cerebral embolic event rates were higher in VP group compared to SP group (p<0.001, p=0.023, p<0.001, respectively). In multivariate analysis, INR monitoring by VP group was found to be an independent predictor of increased risk of bleeding events (OR 2.55, 95% CI 1.64-3.96, p<0.001) and embolism (OR 3.42, 95% CI 1.66-7.04, p=0.001).
Conclusion: INR monitoring by same physician was associated with better TTR and lower rates of adverse events during follow-up. Hence, it is worth encouraging an SP-based outpatient follow-up system at least for where warfarin therapy is the only choice.
Keywords: Anticoagulation; embolism; hemorrhage; international normalized ratio; warfarin.
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