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Background: Effective management of warfarin dose to get therapeutic range of International Normalized Ratio (INR) is complex. The present study was designed to know the quality of warfarin control.
Methods: We consecutively enrolled 113 patients taking warfarin. Two groups of patients were divided according to different settings of therapeutic INR. We compared their time in therapeutic range in these two groups.
Results: Totally 113 patients, with 1976 INR tests, were enrolled. Total follow-up period was 188.4 patient-years. Group A included 25 patients, with mean age 43.4 ± 16.0 years, mean INR 2.96 ± 1.61, and mean warfarin dose 4.69 ± 2.03 mg. Group B included 88 patients with mean age 52.7 ± 16.7 years, mean INR 2.67 ± 2.16, and mean warfarin dose 4.80 ± 2.44 mg. One hundred fifty-four (32.8%) INRs were within the target range of 2.5-3.5 in Group A; whereas 533 (35.4%) INRs were within the target range of 2-3 in Group B. Although the target INR in Group A was set in 2.5 to 3.5, 187 (39.8%) INRs were found in the range of 2-3, which was more than those in the range of 2.5 to 3.5 (39.8% vs 32.8%) in the same group. Moreover, the percentage of INR range from 2-3 in Group A, which was originally set with INR range of 2.5-3.5, was more than the percentage found in Group B (39.8% vs 35.4%) whose INR range was set in 2-3.
Conclusions: Setting an INR target range followed by monitoring it in a specialist clinic is not enough to achieve the ideal target range.