Karnofsky Performance Score-Failure to Thrive as a Frailty Proxy?

Abstract

Background. Among patients listed for kidney transplantation, the Karnofsky Performance Status (KPS) Scale has been used as a proxy for frailty and proposed as a predictor of long-term posttransplant outcomes. The KPS is required by the Organ Procurement and Transplantation Network for all transplants; however, the interrater reliability of KPS reporting in kidney transplant candidates has not been well investigated, and there is concern regarding limitations of using KPS that may influence transplant eligibility. Methods. We performed an observational study using existing Scientific Registry of Transplant Recipients data from 2006 to 2020 to examine the variability, reliability, and trends in the KPS among patients on the kidney transplant waitlist. Results. Our analysis included 8197 kidney transplant candidates with >1 KPS in a 3-mo period. We observed 2-7 scores per patient with an average score of 78.9 (SD = 12, 95% confidence interval, 78.8-79.1). We found substantial variability in KPS reporting, in which 27% of the patients had scores that varied widely with 20-80 points in difference. Interrater reliability in the 10-point scale was poor (30%). When using a condensed 4-category scale (disabled, requires assistance, capable of self-care, normal activity), 38% of patients experienced at least a 1-category shift in their score. Conclusions. The lack of reliability in KPS reporting raises concerns when applying the KPS as a proxy for frailty and a metric to be considered when evaluating candidacy for kidney transplantation.