*Purpose: The AST proposed a toolkit to identify frailty in liver transplant (LT) candidates, including the liver frailty index (LFI) and 6-min walk test (6MWT). Personal activity trackers (PAT) can provide remote and continuous physical activity monitoring. We aimed to compare PAT-collected daily step counts to LFI, 6MWT, and usual gait speed (UGST) in LT candidates, testing their ability to predict death and 90-day readmission or hepatic encephalopathy (HE).

*Methods: Candidates evaluated by LT physical therapist were invited to wear a PAT (FitBit) following outpatient baseline LFI, 6MWT, and UGST assessment. These were compared against step counts collected by PAT for the first week (if ≥4 days; at least 10-h/day). In a subset of patients (n=23), analysis was restricted to days registering the step count for >1000 min along with simultaneous heart rate (HR-steps/day).

*Results: 75 patients, age 55±10, male 64%, MELDNa 17±5, BMI 31±7, were included (EtOH 37%, NASH 32%, HCV 15%, and other 16%). Frailty was present in 25% per LFI, 18% per 6MWT, and 20% per UGST. Agreement between frailty tools was 81-88% (highest in LFI-6MWT). Daily step count was lower in frail vs. non-frail patients, particularly when considering HR-steps/day (Table). Step count also differed between LFI frail, pre-frail [3648 (2057-7067)] and robust [5357 (2815-10574)]; p=0.02. AUROC for frailty diagnosis based on PAT improved when analysis was restricted to HR-steps/day (Table). During follow up there were 9 deaths and 19 hospital admissions (6 for HE). On survival analysis, only UGST predicted mortality (HR=4.7; p=0.03) with a trend for PAT<2500 steps/day (HR=3.6; p=0.07). Frailty by all methods was associated with hospital admission (LFI, HR=2.78, p=0.04; 6MWT, HR=3.4, p=0.02; UGST, HR=5.5, p=0.001; PAT<2500 steps/day, HR=11.2, p<0.001). Notably, only PAT<1000 steps/day predicted HE-related admission (HR=9.9, p=0.02).

*Conclusions: Daily step count from PAT correlated with 3 performance-based frailty tests. Restricting step counts to those paired with heart rate detection for >1000 minutes/day increased frailty diagnostic accuracy. Patients walking <2500 steps/day were at a higher risk for hospital admission, similar to what was found for frail patients identified with any of the validated methods. PAT can help LT centers remotely identify frailty in real-time and better triage prehabilitation efforts.

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