German mHealth App Usability Questionnaire (G-MAUQ) and short version (G-MAUQ-S): Translation and validation study

The use of mobile health applications is increasingly common among the general public and in healthcare systems. With such apps percolating into the classic healthcare sector, the necessity of sound and standardized evaluation grows. The mHealth App Usability Questionnaire (MAUQ) provides a novel and custom-tailored psychometrically validated instrument to capture users’ perception of the usefulness and usability of an mHealth application. So far, this questionnaire is only available in English, Malay and Chinese. The aim of this study was to translate and validate a German version of the MAUQ (G-MAUQ). Further, we developed a short scale with 6 items (G-MAUQ-S) in German. We used the Translation, Review, Adjudication, Pretest and Documentation (TRAPD) method to translate the MAUQ. Subsequently, we assessed content validity with 15 expert ratings and face validity with 15 German speaking mHealth users. To further validate the questionnaire, we used data from 148 participants of an RCT examining symptom checkers in the Emergency Department to assess convergent validity by correlating the G-MAUQ with the German version of the System Usability Scale and discriminant validity by correlating the G-MAUQ with other unrelated questionnaires. Lastly, we developed a short version by assessing item discrimination, factor loadings, correlation with the full scale and construct validity. All but one item showed sufficient content validity with item-level content validity index values between CVI-I = 0.8 and 1.0. Face validity was excellent with item-level face validity index values ranging from FVI-I = 0.87 to 1. Convergent validity was sufficient with r = 0.769, and discriminant validity was sufficient with values between r = −0.014 and r = 0.220. An internal consistency of Cronbach's α = 0.93 demonstrated high reliability. The short scale showed sufficient convergent validity (r = 0.762) and discriminant validity (r between −0.012 and 0.201). A validated and reliable G-MAUQ can be used by researchers and practitioners to assess the usability of mHealth interventions. We also provide the German mHealth App Usability Questionnaire – Short Version (G-MAUQ-S) with six questions to quickly assess the usability of an intervention.