Background: Despite demonstrated efficacy in stroke prevention, warfarin is underused in patients with atrial fibrillation (AF). Reasons for warfarin nonuse are unclear.
Methods: We conducted a retrospective cohort analysis using Ohio Medicaid administrative billing data to ascertain determinants of warfarin use for patients with new-onset nonvalvular AF. The database included data from all institutions, providers, and pharmacies providing services to Ohio Medicaid enrollees. Subjects included all 11699 continuously enrolled fee-for-service recipients of Ohio Medicaid with a new diagnosis of nonvalvular AF between January 1, 1998, and December 31, 2000. We determined incipient warfarin use and presence of risk factors for stroke and hemorrhage by searching claims records for corresponding International Classification of Diseases, Ninth Revision, Clinical Modification codes and National Drug Codes. Univariate and multivariable analyses were performed to examine the association of risk factors with warfarin use.
Results: Only 9.7% of all patients and 11.9% of those without apparent contraindications filled prescriptions for warfarin from 7 days preceding to 30 days after the development of AF. Hypertension and congestive heart failure independently predicted increased warfarin use. Older age (>or=85 years), younger age (<55 years), prior intracranial hemorrhage, prior gastrointestinal hemorrhage, predisposition to falls, alcohol or other drug abuse, renal impairment, and conditions perceived as barriers to compliance predicted decreased warfarin use.
Conclusions: Few in this cohort of Ohio Medicaid patients with incident AF filled prescriptions for warfarin within 30 days of the diagnosis. Several factors, including alcohol or other drug abuse or dependence, psychiatric disease, homelessness or inadequate housing, and lack of a caregiver, were highly prevalent and seemed to bias against warfarin prescribing.