Introduction: Inhalation devices affect both the effectiveness and the therapeutic outcomes in persistent airway obstruction, and the effects are largely independent of the drug(s) assumed. Usability is a complex and comprehensive indicator of inhalation devices' performance. The Global Usability Score (GUS) Questionnaire is an investigational tool designed to assess objectively the patients'-related and unrelated domains of devices' usability.
Methods: The GUS questionnaire was administered to all consecutive COPD patients referring for three months to the Lung Unit of CEMS Specialist Centre (Verona, Italy). The usability of seven Dry Powder Inhalers (DPIs) indicated as appropriate in COPD was tested and compared: Breezhaler, Diskus, Ellipta, Genuair, Nexthaler, Spiromax, and Turbohaler. Patients were divided in two groups, checked separately, according to their DPIs previous experience. A Bayesian Indirect Comparison (IC) model was built to assess "global usability" ranking.
Results: A total of 103 patients were investigated: 74 patients already instructed in DPI use and 29 naive to DPIs. IC analysis proved Ellipta as the device characterized by the highest usability, while Breezhaler the device with the lowest usability in both groups of COPD patients (both with probability > 90%). Moreover, Turbohaler ranked second according to the Bayesian pooling, followed by Diskus, Spiromax, Nexthaler, and Genuair in patients already instructed in DPI use, while the ranking order was not as much well defined in naïve patients, likely due to their too small sample.
Conclusions: Usability is a multifaceted indicator that contributes to assess the factual DPIs' convenience in real life. DPIs are characterized by different levels of real-life usability, which can be checked, compared and ranked by means of the GUS score.
Keywords: COPD; Dry powder inhalers; Global usability score; Inhalation therapy; Usability.