This study describes the prototype testing and clinical validation of the Fit-Frailty App, a fully guided, interactive mobile health (mHealth) app to assess frailty and sarcopenia. This multi-dimensional tool is freely available on the App Store and considers medical history, physical performance, cognition, nutrition, daily function and psychosocial domains. To guide management, a total frailty score and clinical summary of underlying "risk flags" are provided. Our objectives were to examine usability, feasibility, criterion and construct validity.

Cross-sectional

Outpatient geriatric medicine clinic

Community-dwelling older adults, age 65 years or older

The primary outcome of the clinical validation study was criterion validity. A research nurse administered the Fit-Frailty App during a routine clinic appointment. Clinicians simultaneously completed a paper-based frailty index (FI) tool with similar items from a comprehensive geriatric assessment (FI-CGA). Total scores for both assessments were computed using the cumulative deficits frailty index scoring method. Intraclass and Pearson correlation coefficients and 95% CIs were calculated to examine criterion validity. Secondary outcomes were construct validity, feasibility (eg, completion rates, safety occurrences, resources) and usability (eg, ratings on ease of use, time to complete the app).

In the clinical validation study (n=75, mean age 79.2, SD=7.0, 53% female), the mean total Fit-Frailty App score was 0.33 (SD=0.13) with 73% of our sample considered frail or severely frail. The app presented comparable results to FI-CGA (moderate to good validity; ICC=0.65, 95%CI=0.50–0.76) with a strong association between the measures (r=0.74, 95%CI=0.62–0.83). In our prototype and clinical cohorts, the app had a 100% completion rate with no safety occurrences and had high usability ratings.

The Fit-Frailty App is a feasible and valid tool that can be used in research and clinical settings to comprehensively assess frailty and sarcopenia by non-geriatricians and could assist with developing targeted interventions.