Development and validation of the German version of the Mobile Application Rating Scale (MARS-G)

Background: Evidence for the efficacy of mobile health applications (MHA) to foster healthy behavior, to prevent the onset of disease, to manage and cure disease as well as to assist with rehabilitation is rapidly growing. However, most mobile health apps lack efficacy data, and user star ratings in app stores are limited in their objectivity. Objective: Systematic assessments are highly needed to make pro and cons of MHA use transparent and to develop quality standards. The mobile application rating scale (MARS) is such an assessment tool, but it’s not available in German yet. This study addresses that gap. Methods: The original 19-item version of the mobile app rating scale (MARS) was forward and backward translated twice, resulting in the MARS-German (MARS-G). App description items were extended (e.g. methodological background, data handling, etc.). 104 MHA were rated twice by eight independent bilingual researchers with the German and English MARS version. The internal consistency, validity and reliability of both scales were assessed. Mokken scale analysis was used to investigate the scalability of the overall scores. Results: The retranslation did not result in differences. The properties of the MARS-G are comparable to the original English version of the scale. Internal consistency is good for all subscales: Omega ranged from .72 to .91. Correlations between the scales of the German and English version reached from r=.93 to r=.98. Scalability of MARS (H=.50) and MARS-G are (H=.48) good. Conclusions: The MARS-G is a reliable and valid tool for experts and stakeholders to assess the quality of health apps in German speaking populations. Using the overall score gives a reliable quality estimation. Further studies are needed to assess the factorial structure of MARS and MARS-German. Clinical Trial: Not needed is a translation of a questionnaire, no participants involve