The independent association between serum uric acid and graft outcomes after kidney transplantation

Abstract

Background: Improving long-term outcomes of kidney transplantation depends on identifying novel risk factors that lead to poor outcomes. We sought to evaluate the predictive value of mean uric acid (UA) level during the first 6 months posttransplant for graft survival and function.

Methods: Two hundred twelve recipients of living donor kidneys transplanted during January 2000 to December 2001 were included. The study outcome included graft and patient survival and graft function at 1 year posttransplant. Regression models were used to adjust for the confounding variables including graft function during first 6 months.

Results: During 68.3 + or - 27.2 months follow-up, UA level (mg/dL) and hyperuricemia (n=45) were associated with graft loss (hazard ratio [HR]=1.26, P=0.026, 95% confidence interval [CI]=1.03-1.53, and HR=1.92, P=0.029, 95% CI=1.1-3.4, respectively) independent of graft function and other confounders. UA also seemed to be associated with risk of death with borderline significance (HR=1.2, P=0.096, 95% CI=0.97-1.46). Examining the predictive value for graft function, UA level and hyperuricemia were independent predictors of 1-year serum creatinine (beta=0.10, P=0.013, 95% CI=0.02-0.18, and beta=0.25, P<0.04, 95% CI=0.01-0.49, respectively). Similarly, both were associated with 1-year estimated glomerular filtration rate (beta=-3.9, P<0.001, 95% CI=-5.7 to -1.5 for UA, and beta=-7.6, P<0.02, 95% CI=-13.6 to -1.5 for hyperuricemia). Notably, these associations were all independent of renal function during first 6 months.

Conclusion: The results of this study suggest that mean UA level during the first 6 months posttransplant is an independent predictor of long-term graft survival and short-term graft function. Further investigations are needed to evaluate its causal association with chronic allograft injury and cardiovascular disease.