The Global Usability Score: A Novel Comprehensive Tool for Assessing, Ranking, and Compare Usability of Inhalers in Patients Requiring Airway Treatments

Introduction: The inhalation route is the best choice for respiratory drug delivery, but benefits to patients are strictly related to the proper use of inhalers. The role of patients’ view point (such as: their intuitivity, preference, acceptance, and satisfaction) were extensively investigated, even if other factors, unrelated to their personal beliefs, can further affect inhaler usability. Aim: to define a specific tool for easily assessing, ranking, and comparing the real usability of whatever inhaler by a single, comprehensive score, also based on objective measurements. Methods: A specific, anonymous questionnaire was validated. The Questionnaire consists of four main sections (Introductory; Assessing Track; Global Score calculation, Patient’s personal data). Questions are twenty-seven, all scored: twenty-two addressed to the patient, and five to the expert nurse, who has to conduct the independent assessments. The sum of the eight sub-scores of the Assessing Track will represent the final Global Usability Score- GUS, which ranges 0-50 points for each inhaler; higher the GUS value, higher the real usability will be. Results: the comprehension of all questions at their first reading was >97% in the final version of the GUS Questionnaire, for both patients and nurses participating to the questionnaire development. Discussion: usability of inhalers is a complex and multifaceted issue. When assessing usability, it should be taken into account that the role of patients’ beliefs differently integrates the role of other objective determinants which are unrelated to the sole patients’ viewpoint. Terms like intuitivity, preference, acceptability, or satisfaction should not be used as synonyms for usability, because too related to the patients’ subjectivity only. Conclusions: the Global Usability Score 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.