Performance-based frailty tools capture distinct risk phenotypes in kidney transplant candidates: A comparative...

Frailty predicts adverse outcomes in kidney transplant candidates, but it remains unclear whether different frailty tools identify the same or distinct at-risk patients. In this retrospective cohort study, 953 kidney transplant candidates listed between 2018 and 2022 underwent frailty assessment using both the Fatigue, Resistance, Ambulation, Illnesses, Weight Loss (FRAIL) scale screening and the Short Physical Performance Battery (SPPB) screening test. In a subset with available computed tomography scan imaging, body composition was analyzed using artificial intelligence-based tools. Frailty prevalence differed by instrument: 6.2% using the FRAIL scale screening vs 24% using the SPPB screening test. Waitlist mortality occurred in 9.5% (91/953) of candidates. Both tools independently predicted waitlist mortality (FRAIL scale screening test: adjusted hazard ratio, 2.38; 95% CI, 1.34-4.20; P = .003 and SPPB screening test: adjusted hazard ratio, 1.66; 95% CI, 1.07-2.60; P = .025). The SPPB screening test-defined frailty showed stronger associations with posttransplant outcomes, including longer hospital stays and 30-day and 1-year readmissions. A computed tomography scan analysis revealed that SPPB screening test-defined, but not FRAIL scale screening test-defined, frailty was associated with lower muscle density and increased visceral adiposity, suggesting a mechanistic basis. The FRAIL scale screening test and SPPB screening test captured distinct dimensions of frailty with complementary strengths. The FRAIL scale screening test better reflected symptom burden and candidates at risk for waitlist mortality, whereas the SPPB screening test was more closely associated with posttransplant complications. Results support systematic use of both instruments to optimize risk stratification and identify candidates who may benefit from targeted prehabilitation.