Many patients with asthma use their inhalers incorrectly, which can lead to sub-optimal asthma control and an increased risk of exacerbations. The Accuhaler/Diskus and Turbuhaler are arguably two of the most commonly used dry powder inhalers worldwide.

A systematic literature review (SLR) was conducted to assess the impact of inhalation errors with these dry powder inhalers on clinical outcomes in asthma. Database searches were conducted in MEDLINE, Embase and proceedings from scientific conferences. Observational studies in adults and adolescents with asthma, reporting data for Accuhaler/Diskus and Turbuhaler devices and at least one outcome of interest, were included. Dual-independent screening and validation of studies was performed.

The search identified 35 studies. A range of inhaler errors was observed across studies and devices. In 8 out of the 9 studies that involved the two devices, the percentage of overall inhaler error rates was numerically (7 studies) or significantly (1 study) higher for Turbuhaler than Diskus, ranging from 3.7% to 71.9% for Diskus and 1.2%–83% for Turbuhaler. Critical errors, reported in three studies using similar definitions, ranged from 20% to 43% for Diskus and 32%–100% for Turbuhaler. Five studies reported a significant association between inhaler errors and worse asthma control, while one showed no difference.

This SLR identified a large range of inhaler errors with both devices. Across devices, a better inhalation technique was associated with better asthma outcomes. This systematic review confirms the importance of patients using their inhalers correctly as an integral part of achieving optimal asthma outcomes.