Area-level Predictors of Medication Nonadherence among U.S. Medicaid Beneficiaries with Lupus: A Multilevel Study.

BACKGROUND: Adherence to hydroxychloroquine (HCQ) among patients with systemic lupus erythematous (SLE) is suboptimal. Individual-level factors, including younger age and non-white race/ethnicity, have been implicated; contextual factors have not been explored.

METHODS: We identified SLE patients with new use of HCQ (no use in >6 months) in Medicaid (2000-2010) from 28 U.S. states. We required 12 months of continuous enrollment with complete drug dispensing data and measured adherence using the proportion of days covered (PDC). We identified individual-level variables from Medicaid, zip code, county and state-level sociodemographic variables from the American Community Survey and health resources from Area Health Resources Files. We used 4-level hierarchical multivariable logistic regression models to examine odds (OR (95% Credible Interval)) of adherence (PDC >80%) vs. nonadherence.

RESULTS: Among 10,268 HCQ initiators with SLE, 15% were adherent. After adjusting for individual-level characteristics, we observed lower odds of adherence in zip codes with higher percentages of black individuals (highest tertile OR 0.81 (0.69-0.96) vs. lowest). This association persisted after controlling for zip code educational attainment, percent below federal poverty level (FPL), urbanicity and healthcare resources. We did not find statistically significant associations with zip code-level percent Hispanic, percent White, education or percent below FPL. Odds of adherence were higher in counties with more hospitals (OR 1.30 (1.07-1.58).

CONCLUSIONS: Among Medicaid beneficiaries with SLE, we observed significant effects of racial composition and hospital concentration on HCQ adherence. Interventions that acknowledge and address contextual factors should be considered to reduce high rates of nonadherence in vulnerable populations. This article is protected by copyright. All rights reserved.