Clinical Predictors of Warfarin Response Among Patients with Atrial Fibrillation: Evidence from the Middle Eastern JoFib Study

OBJECTIVES: To describe clinical factors predictive of warfarin response in atrial fibrillation (AF) patients and to evaluate its association with adverse outcomes. METHODS: Patients in the Middle Eastern JoFib study, a prospective, multicenter registry of AF patients, using warfarin with at least one international normalized ratio (INR) reading, were enrolled. We used the most recent INR as a measure of warfarin control. RESULTS: Out of the total 2020 patients, 544 (26.9%) were using warfarin. Multivariable logistic regression analysis demonstrated that heart failure (adjusted OR 0.55, 95%CI 0.36-0.86) and increasing HAS-BLED score (adjusted OR 0.73, 95%CI 0.58-0.92) decreased the odds of having a therapeutic INR. Chronic kidney disease (adjusted OR 3.11, 95%CI 1.46-6.62), heart failure (adjusted OR 2.37, 95%CI 1.4-4.01), and cancer (adjusted OR 2.48, 95%CI 1.03-6.01) were independently predictive of having INR less than 2.0. The first episode of AF was independently predictive of having INR above 3.0 (adjusted OR 2.48, 95%CI 1.39-4.42). Multivariable Cox regression analysis demonstrated that INR below the therapeutic range (aHR 4.36, 95%CI 2.19-8.68) and INR above the therapeutic range (aHR 3.03, 95%CI 1.33-6.92) were predictive of all-cause mortality. Below-range INR also predicted cardiovascular mortality (aHR 3.69, 95%CI 1.66-8.16). CONCLUSION: Clinical factors predictive of sub-optimal INR in Middle Eastern AF patients using warfarin include chronic kidney disease, heart failure, cancer, high HAS-BLED score, and first episode of AF. Furthermore, sub-optimal INR is predictive of all-cause and cardiovascular mortality.