Available online 2 July 2025

What is already known about this topic?

Poor adherence to ICS/LABA is common in patients with severe asthma and is associated with poorer clinical outcomes. However, the impact of biologic initiation on adherence and downstream clinical outcomes whilst on biologics, remains unclear.

What does this article add to our knowledge?

The introduction of biologics had little impact on population level adherence, however there were substantial changes in individual patients. Poorer adherence to ICS/LABA was associated with higher exacerbation rates and FeNO for biologic treated patients longer-term.

How does this study impact current management guidelines?

Regular counselling on the importance of inhaled therapy adherence is required for patients receiving biologics. Poorer adherence is associated with worse clinical outcomes but is potentially modifiable through novel interventions.

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.

Retrospective cohort study of adults attending the Northern Ireland Regional Severe Asthma centre between September 2015 and November 2021. 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 pre- and post-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 sub-optimal adherence prior to biologic initiation. This was associated with higher deprivation (43.1% vs. 25.2%; p=0.012) and fractional exhaled nitric oxide (FeNO) (50 vs 32ppb; p=0.043). Population-level MPRs were stable during the study, however adherence varied for individual patients. 69 (33.3%) patients had poor adherence one-year post-biologic. Although a substantial reduction in exacerbation rates were seen for both groups post-biologic initiation, those with good adherence had an additional 17.4% (95% CI: 2.2%, 30.2%) reduction in exacerbations compared to 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.

Asthma

Treatment Adherence and Compliance

Biological Therapy

Asthma Control Questionnaire 5

Fractional Exhaled Nitric Oxide

Forced Expiratory Volume in 1 Second

Healthcare Resource Utilisation

Inhaled Corticosteroids

Long-acting β2-agonist

Leukotriene Receptor Antagonists

Multiple Deprivation Measure

Medication Possession Ratio

short-acting beta-2 agonist

© 2025 Published by Elsevier Inc. on behalf of the American Academy of Allergy, Asthma & Immunology