Pre-Kidney Transplant Lower Extremity Impairment and Post-Kidney Transplant Mortality

Prediction models for post-kidney transplantation mortality have had limited success (C-statistics ≤0.70). Adding objective measures of potentially modifiable factors may improve prediction and, consequently, kidney transplant (KT) survival through intervention. The Short Physical Performance Battery (SPPB) is an easily administered objective test of lower extremity function consisting of three parts (balance, walking speed, chair stands), each with scores of 0-4, for a composite score of 0-12, with higher scores indicating better function. SPPB performance and frailty (Fried frailty phenotype) were assessed at admission for KT in a prospective cohort of 719 KT recipients at Johns Hopkins Hospital (8/2009 to 6/2016) and University of Michigan (2/2013 to 12/2016). The independent associations between SPPB impairment (SPPB composite score ≤10) and composite score with post-KT mortality were tested using adjusted competing risks models treating graft failure as a competing risk. The 5-year posttransplantation mortality for impaired recipients was 20.6% compared to 4.5% for unimpaired recipients (p < 0.001). Impaired recipients had a 2.30-fold (adjusted hazard ratio [aHR] 2.30, 95% confidence interval [CI] 1.12-4.74, p = 0.02) increased risk of postkidney transplantation mortality compared to unimpaired recipients. Each one-point decrease in SPPB score was independently associated with a 1.19-fold (95% CI 1.09-1.30, p < 0.001) higher risk of post-KT mortality. SPPB-derived lower extremity function is a potentially highly useful and modifiable objective measure for pre-KT risk prediction.