Investigating the Association Between Biologic Initiation and Medication Adherence in Severe Asthma: An Analysis of Linked Data.

Abstract

Poor adherence to inhaled therapy is common among patients with asthma. Findings from previous studies exploring inhaled corticosteroid (ICS) adherence in biologic-treated populations are inconsistent and have not investigated the long-term outcomes. To assess the long-term impact of introducing biologics on ICS/long-acting β₂-agonist (LABA) adherence and to investigate the effect of poor ICS/LABA adherence on clinical outcomes among biologic-treated patients. A retrospective cohort study of adults who attended the Northern Ireland Regional Severe Asthma center between September 2015 and November 2021 was performed. Medication possession ratios (MPRs) for ICS/LABA medication were calculated using community dispensing records. Good adherence was defined as an MPR ≥75%. We compared adherence before and after biologic initiation, examined the correlates of adherence, and used multivariable longitudinal models to assess the impact of adherence on asthma outcomes. Of 207 included patients, 58 (28.0%) had suboptimal adherence before biologic initiation. This was associated with higher deprivation (43.1% vs 25.2%; P = .012) and fractional exhaled nitric oxide (50 vs 32 parts per billion; P = .043). Population-level MPRs were stable during the study; however, adherence varied for individual patients. A total of 69 (33.3%) patients had poor adherence 1 year after biologic initiation. Although a substantial reduction in exacerbation rates was seen for both groups after biologic initiation, those with good adherence had an additional 17.4% (95% confidence interval: 2.2%, 30.2%) reduction in exacerbations compared with those with poor adherence. We found no difference in asthma symptoms or lung function. The introduction of biologics had little impact on population-level adherence; however, there were substantial changes for individual patients. Good adherence to ICS/LABA was associated with lower exacerbation rates among biologic-treated patients with severe asthma.