Prevalence of frailty in patients referred to the kidney transplant waitlist

Abstract

Background: Comparisons between frailty assessment tools for waitlist candidates are a recognized priority area for kidney transplantation. We compared the prevalence of frailty using three established tools in a cohort of waitlist candidates. Methods: Waitlist candidates were prospectively enrolled from 2016-2020 across five centers. Frailty was measured using the Frailty Phenotype (FP, as well as a 37 variable Frailty Index (FI), and the Clinical Frailty Scale (CFS). The FI and CFS were dichotomized using established cut-offs. Agreement was compared using kappa coefficients. Area under the receiver operator characteristic curves were generated to compare the FI and CFS (treated as continuous measures) to the FP. Unadjusted associations between each frailty measure and time to death or waitlist withdrawal were determined using an unadjusted Cox proportional hazards model. Results: Of 542 enrolled patients, 64% were male, 80% were white, and the mean age was 54+/-14. The prevalence of frailty by the FP was 16%. The mean FI score was 0.23+/-0.14 and the prevalence of frailty was 38% (score of >0.25). The median CFS score was 3 (IQR 2,3), and the prevalence was 15% (score of ≥4). Kappa values comparing the FP to the FI (0.438) and CFS (0.272) showed fair to moderate agreement. Area under the ROC curve for the FP and FI/CFS were 0.86 (good) and 0.69 (poor) respectively. Frailty by the CFS (HR 2.10; 95% CI (1.04, 4.24) and FI (HR 1.79; 95% CI 1.00,3.21) was associated with death or permanent withdrawal. The association between frailty by the FP and death/withdrawal was not statistically significant (HR 1.78; CI 0.786, 3.71). Conclusion: Frailty prevalence varies by measurement tool used, and agreement between these measurements is fair to moderate. This has implications for determining the optimal frailty screening tool for use in those being evaluated for kidney transplant.