OBJECTIVES: Preference and usability of Inhalation devices, affect per sé the effectiveness and the outcomes of treatment in persistent airway obstruction, independently of the drug(s) administered. The Global Usability Score (GUS) Questionnaire was used to assess, rank, and compare the real usability of six devices.

METHODS: The questionnaire was administered to consecutive patients suffering from persistent asthma or COPD, from October to December 2017. Six devices were compared: Breezhaler, Diskus, Ellipta, Nexthaler, Spiromax, and Turbohaler. The predicted power of GUS was measures using ROC curve and the area under the curve (AUC) was calculated. A Bayesian Indirect Comparison (IC) model was built to assess the usability and to rank each device in a “global usability” classification. The cost-of-usability, defined as the cost due to nurse-training for ensuring a proper actuation and the device cost, was also calculated for each device.

RESULTS: CONCLUSIONS: The usability of inhalers is a complex and multifaceted issue that should include the role of patients’ beliefs and other objective determinants which are unrelated to the sole patients’ viewpoint. The GUS represents the first comprehensive score for assessing, ranking, and comparing objectively the contribution of all main components of inhaler usability, and then provide an effective and motivated standard of choice.