Ethnic variability in warfarin maintenance in the community setting: a population-based study in a managed care environment in Israel.

Background: Ethnicity has been associated with variance in warfarin treatment regimens in various settings.

Objectives: To determine whether ethnicity is associated with variance in patient management in Israel.

Methods: Data were extracted from the electronic patient records of Clalit Health Services clinics in the Sharon Shomron region. The study group comprised all patients treated with warfarin who performed international normalized ratio tests for at least 6 months in 2003. The proportion of tests of each patient within the target range was calculated, as was the crude average rates and 95% confidence intervals for Jewish and Arab patients. The data were then stratified by patient's gender and age, specialty of the attending physician, and the country where the physician studied medicine.

Results: We identified 2749 Jews and 293 Arabs who met the inclusion criteria of the study. The crude average rate of patients' INR tests within the target range was 62.3% among Jews (95% CI 61.5-63.1) and 52.7% (95% CI 49.9-55.5) among Arabs. When stratified by gender, age, and the treating physician's specialty and country of education, the stratum-specific rates among Jewish patients were consistently higher than among Arabs.

Conclusions: These results suggest that cultural differences regarding adherence to recommendations for drug therapy in addition to genetic factors may be associated with this variance.