Medication Nonadherence Is Associated With Increased Subsequent Acute Care Utilization Among Medicaid Beneficiaries With Systemic Lupus Erythematosus

OBJECTIVE: We examined whether nonadherence to hydroxychloroquine (HCQ) or immunosuppressive medications (ISMs) was associated with higher subsequent acute care utilization among Medicaid beneficiaries with systemic lupus erythematosus (SLE). METHODS: We utilized US Medicaid data from 2000-2006 to identify adults ages 18-64 years with SLE who were new users of HCQ or ISMs. We defined the index date as receipt of HCQ or ISMs without use in the prior 6 months. We measured adherence using the medication possession ratio (MPR), the proportion of days covered by total days' supply dispensed, for the 1-year post-index date. Our outcomes were all-cause and SLE-related emergency department (ED) visits and hospitalizations in the subsequent year. We used multivariable Poisson regression models to examine the association between nonadherence (MPR <80%) and acute care utilization, adjusting for sociodemographics and comorbidities. RESULTS: We identified 9,600 HCQ new users and 3,829 ISM new users with SLE. The mean ± SD MPR for HCQ was 47.8% ± 30.3% and for ISMs was 42.7% ± 30.7%. Seventy-nine percent of HCQ users and 83% of ISM users were nonadherent (MPR <80%). In multivariable models, among HCQ users, the incidence rate ratio (IRR) of ED visits was 1.55 (95% confidence interval 95% CI 1.43-1.69) and the IRR of hospitalizations was 1.37 (95% CI 1.25-1.50), comparing nonadherers to adherers. For ISM users, the IRR of ED visits was 1.64 (95% CI 1.42-1.89) and of hospitalizations was 1.67 (95% CI 1.41-1.96) for nonadherers versus adherers. CONCLUSION: In this cohort, nonadherence to HCQ and ISMs was common and was associated with significantly higher subsequent acute care utilization.