Pretransplant serum phosphate levels and outcomes after kidney transplantation

The relation between serum phosphate control while on dialysis and kidney transplant outcomes is uncertain. Our study assessed the effect of pretransplant serum phosphate levels (PTxP) on kidney transplant outcomes.

Hemodialysis patients included in the Dialysis Morbidity and Mortality Study of the US Renal Data System, undergoing kidney transplantation were studied (n=801). Delayed graft function (DGF) and graft failure as a function of PTxP, were assessed using multivariable logistic and Cox regression models.

The within-quartile medians (interquartile range) of PTxP were 4.2 (3.7-4.5), 5.4 (5.1-5.7), 6.4 (6.1-6.8) and 8.5 (7.7-9.7) mg/dL. The adjusted odds ratio (OR) for DGF was significantly elevated for the fourth vs. first PTxP quartiles (OR=1.68; 95% confidence interval [95% CI], 1.05-2.71). Restricting the cohort to patients transplanted prior to the publication of the KDOQI bone metabolism and disease guidelines, PTxP measured within 1-year of transplant, or deceased donor recipients generally showed similar results. The adjusted hazard ratios for death-censored graft failure increased across PTxP quartiles (p for trend = 0.015).

Higher PTxP is associated with an increased risk of adverse kidney allograft outcomes including DGF and death-censored graft failure. This suggests an important additional benefit of optimizing phosphate control in patients awaiting kidney transplantation while on dialysis.