Serum phosphate measured at 6 and 12 months after successful kidney transplant is independently associated with subsequent graft loss.

OBJECTIVES Serum phosphate concentrations have been shown to predict graft loss in prevalent, but not incident, kidney transplant populations. The reasons for this are unknown. We investigated whether serum phosphate at 6 or 12 months posttransplant was associated with graft loss in the same cohort. MATERIALS AND METHODS Data were collected for 325 patients transplanted and followed up at a single center (1996-2004). The association between serum phosphate at 6 and 12 months posttransplant and graft failure was analyzed. RESULTS Univariable associations with death-censored graft failure were seen for serum phosphate at 6 and 12 months (hazard ratio [HR] 1.33; 95% confidence interval [CI] 1.20-1.48; P < .001, and HR 1.40; CI 1.27-1.54; P < .001). On bivariable analysis (phosphate at 6 vs 12 mo), a significant association remained for both variables and increased graft failure rate (HR 1.19; CI 1.07-1.34; P = .002, and HR 1.37; CI 1.21-1.55; P < .001). These associations persisted in multivariable models (HR 1.27; CI 1.07-1.51; P = .007, and HR 1.34; CI 1.14-1.57; P < .001 for phosphate at 6 and 12 mo). CONCLUSIONS Serum phosphate at 6 and 12 months posttransplant is an independent predictor of graft loss. Any future trial designed to investigate the benefits of phosphate lowering should consider recruiting patients as early as 6 months posttransplant.