Real-world impact of non-clinical inhaler regimen switches on asthma or COPD: a systematic review

Background: Switching inhaler regimens can be driven by poor disease control, but also by non-clinical factors, such as cost and environmental impact. The consequences of switching for non-clinical reasons are largely unclear. Objective: To systematically review the real-world consequences of switching inhaler regimens for non-clinical reasons in asthma and/or COPD patients. Methods: Embase, MEDLINE, EBM Reviews and EconLit were searched to 21st November 2020. Conference searches and reference checking were also performed. Real-world studies of asthma and/or COPD patients undergoing a switch in inhaler regimen for any reason apart from clinical need were included. Two reviewers screened and extracted data. Key outcomes included symptom control, exacerbations and patient-doctor relationships. Prospero: CRD42021230427. Results: 8,958 records were screened and 21 studies included. Higher quality (matched comparative) studies were prioritised. Five matched studies (six datasets) reported on symptom control: five datasets (N=7,530) with unclear patient consent reported improved disease control following switching; and one dataset (N=1,648) with non-consented patients reported significantly worsened disease control. Three matched studies (5 datasets, N=10,084) reported on exacerbation rate ratios; results were heterogeneous depending on the definition used. Two studies (N=137) reported that switching inhaler regimens could have a negative impact on the doctor-patient relationship, especially when the switches were non-consented. Study quality was generally low. Conclusion: Switching inhaler regimens is a complex issue that can have variable clinical consequences and can harm the patient-doctor relationship. Limited high-quality evidence was identified, and study designs were heterogeneous. A robust framework is needed to guide the personalised switching of inhalers.