Physical Frailty and Functional Status in Kidney Transplantation: A Systematic Review.

Background: Frailty and functional decline are being recognized as important conditions in kidney transplant candidates. However, the ideal measures of functional status and frailty remain unknown as there is not a complete understanding of the relationship between these conditions and important post-transplant outcomes. Objective: The objective was to examine the association between different measures of frailty and functional status evaluated before or at the time of transplant with adverse clinical outcomes post-transplantation. Design: This study is a systematic review. Setting: Observational studies including cohort, case-control, or cross-sectional studies examining the effect of frailty and functional status on clinical outcomes. There were no restrictions on type of setting or country of origin. Patients: Adults who were waitlisted for kidney transplant or had received a kidney transplant. Measurements: Data including demographic information (eg, sample size, age, country), assessments of frailty or functional status and their domains, and outcomes including mortality, transplantation, graft loss, delayed graft function and hospital readmission were extracted. Methods: A search was performed in Medline, Embase, and Cochrane Central Register for Controlled Trials. Studies were included from inception to February 7, 2023. The eligibility of studies was screened by 2 independent reviewers. Data were presented by frailty/functional status instrument and clinical outcome. Point estimates and 95% confidence intervals from fully adjusted statistical models were reported or calculated from the raw data. Results: A total of 50 studies were identified, among which 36 unique instruments were found. Measurements of these instruments occurred mostly at time of kidney transplant, transplant evaluation, and waitlisting. The median sample size of studies was 457 patients (interquartile range = 183-1760). Frailty and lower functional status were associated with an increased risk for mortality. Similar trends were observed among other clinical outcomes such as graft loss and rehospitalization. Limitations: The heterogeneity in measurement instruments, study designs, and outcome definitions prevents pooling of the data. Selection bias and the validity of data collection could not be ascertained for some studies. Conclusion: Frailty and functional status measures are important predictors of post-kidney transplant outcomes. Further studies are needed to evaluate the best instruments to assess frailty and functional status, and importantly, interventional studies are needed to determine whether prehabilitation strategies can improve post-transplant outcomes. Registration PROSPERO: CRD42016045251.