A Messaging App Empowering Lifestyle Modification in Chronic Kidney Disease (LINE Official Account "Kidney Lifestyle"): Platform Development and Usability Study.

Background: Regular lifestyle modification is crucial for chronic kidney disease (CKD) management; yet, older patients often struggle to sustain behavior change and rely on support from their significant others such as family caregivers or partners. In such cases, both members of the dyad require accessible, jointly usable tools to maintain healthier behaviors over time. Given the ubiquity of instant messaging platforms, a digital intervention delivered via such a platform offers strong potential to empower CKD dyads in active lifestyle modification. Objective: Guided by the Digital Dyadic Empowerment Framework, this study aimed to develop, optimize, and test the usability of a digital platform named "Kidney Lifestyle," using the LINE Official Account (OA) and an integrated extended app to facilitate collaborative lifestyle modification among CKD dyads. Methods: We adopted a three-phase Agile-based development cycle: (1) iterative development and trial use, (2) heuristic evaluation, and (3) usability testing. In phase 1, the platform prototype was codeveloped with health care professionals and trialed by CKD dyads who provided feedback on interface clarity, ease of use, acceptance, intention to continue usage, and overall satisfaction. In phase 2, multidisciplinary experts conducted heuristic evaluations, rating compliance with Nielsen's 10 usability principles and suggesting improvements. In phase 3, experienced CKD dyads from phase 1 performed 6 representative tasks using the platform. Task success rates, completion times, and operational errors were recorded, and usability perceptions were assessed using the After-Scenario Questionnaire (1-7) and the System Usability Scale (0-100). Results: In phase 1, 10 CKD dyads (19 individuals) reported high acceptance (mean overall satisfaction 4.1/5), valuing real-time interaction, convenient health data monitoring, and educational resources. In phase 2, 5 experts found high usability compliance (89%-93%) but noted navigation complexity and the need for more interactive feedback. In phase 3, usability testing with 5 dyads showed high task success (60%-100%) and short completion times (1-5 minutes). Extended app tasks used for structured self-monitoring achieved higher satisfaction, reflecting simpler navigation than tasks within the LINE OA (mean After-Scenario Questionnaire 5.64 vs 3.87). Navigation difficulties within LINE OA were likely due to multilayered menus and limited customization. The average System Usability Scale was 67.5, indicating marginally acceptable usability. Conclusions: The LINE-based digital dyadic empowerment platform "Kidney Lifestyle" demonstrated promising usability and engagement. It has clinical potential to improve CKD control by extending health education, enabling continuous self-monitoring, and allowing clinicians to track patients' daily living conditions. To enhance effectiveness, future work should include a larger-scale feasibility trial while pursuing ongoing platform optimization, specifically by simplifying navigation pathways, adding a return option, and improving interactive feedback. The platform is now publicly accessible via LINE ID search, as provided in phase 1 results.