The pharmacy-level asthma medication ratio and population health

Community pharmacies may be positioned for an increased role in population health. We sought to develop a population-level measure of asthma medication fills and assess its relationship to asthma-related utilization.

We conducted a retrospective, ecological study (2010-2012). Medication data from a chain of pharmacies (n = 27) within 1 county were used to calculate a Pharmacy-level Asthma Medication Ratio (Ph-AMR), defined as controller fills divided by controller plus rescue fills. Higher values are superior because they indicate more controller compared with rescue fills. The outcome was the asthma-related utilization rate among children in the same census tract as the pharmacy, calculated by dividing all emergency visits and hospitalizations by the number of children in that tract. Covariates, including ecological measures of poverty and access to care, were used in multivariable linear regression.

Overall, 35 467 medications were filled. The median Ph-AMR was 0.53 (range 0.38-0.66). The median utilization rate across included census tracts was 22.4 visits per 1000 child-years (range 1.3-60.9). Tracts with Ph-AMR <0.5 had significantly higher utilization rates than those with Ph-AMR ≥0.5 (26.1 vs 9.9; P = .001). For every 0.1 increase in Ph-AMR, utilization rates decreased by 9.5 (P = .03), after adjustment for underlying poverty and access. Seasonal variation in fills was evident, but pharmacies in high-utilizing tracts filled more rescue than controller medications at nearly every point during the study period.

Ph-AMR was independently associated with ecological childhood asthma morbidity. Pharmacies may be a community-based leverage point for improving population-level asthma control through targeted interventions.