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The influence of socioeconomic status on selection of anticoagulation for atrial fibrillation

Sholzberg M, Gomes T, Juurlink DN, Yao Z, Mamdani MM, Laupacis A. PLoS One. 2016; 11(2):e0149142.

Importance — Without third-party insurance, access to marketed drugs is limited to those who can afford to pay. We examined this phenomenon in the context of anticoagulation for patients with nonvalvular atrial fibrillation (NVAF).

Objective — To determine whether, among older Ontarians receiving anticoagulation for NVAF, patients of higher socioeconomic status (SES) were more likely to switch from warfarin to dabigatran prior to its addition to the provincial formulary.

Design, Setting and Participants — Population-based retrospective cohort study of Ontarians aged 66 years and older, between 2008 and 2012.

Exposure — Socioeconomic status, as approximated by median neighborhood income.

Main Outcomes and Measure — We identified two groups of older adults with nonvalvular atrial fibrillation: those who appeared to switch from warfarin to dabigatran after its market approval but prior to its inclusion on the provincial formulary (“switchers”), and those with ongoing warfarin use during the same interval (“non-switchers”).

Results — We studied 34,797 patients, including 3183 “switchers” and 31,614 “non-switchers”. We found that higher SES was associated with switching to dabigatran prior to its coverage on the provincial formulary (p<0.0001). In multivariable analysis, subjects in the highest quintile were 50% more likely to switch to dabigatran than those in the lowest income quintile (11.3% vs. 7.3%; adjusted odds ratio 1.50; 95% CI 1.32 to 1.68). Following dabigatran’s addition to the formulary, the income gradient disappeared.

Conclusions and Relevance — We documented socioeconomic inequality in access to dabigatran among patients receiving warfarin for NVAF. This disparity was eliminated following the drug’s addition to the provincial formulary, highlighting the importance of timely reimbursement decisions.

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Keywords: Equity in health care Atrial fibrillation Drug prescribing behaviour Drugs (cardiovascular)