High concentrations of retinol binding protein (RBP) are found in the urine of patients with tubulointerstitial injury. We evaluated the predictive value of urinary RBP (RBPu) for development graft dysfunction after kidney transplantation.
Methods: Serum creatinine and RBPu were prospectively measured at months 3, 6, and 12 in 221 kidney transplant patients. Baseline graft function was defined as the lowest serum creatinine value during the first 3 months after transplantation. Graft dysfunction was assessed at 1 year as a >-20% or >-30% change in the inverse creatinine ((Delta)1/Cr) compared to baseline value at month 3.
Results: Among 183 patients with normal graft function (Cr </= 1.6 mg/dL) the mean (Delta)1/Cr from month 3 to 12 was -17 +/- 22% (-80% to + 44%). Using a receiver operating characteristic (ROC) analysis, concentrations higher than 0.6 mg/L showed the best predictive value for diagnosis of graft dysfunction at 1 year. Mean (Delta)1/Cr from month 3 to 12 was -13 +/- 20% for those with RBP < 0.6 mg/L vs -20 +/- 23% in those with RBPu > 0.6 mg/L (95% CI = -13% to -1.3%, P =.018). The percentage of patients with >-20% or >-30% (Delta)1/Cr was higher among patients with RBPu > 0.6 mg/L (34% vs 47%, P =.042; 21% vs 34%, P =.035). RBPu > 0.6 mg/L was the only variable independently associated with >-30% (Delta)1/Cr at 1 year, with an odds ratio (OR) of 1.95 (95% CI 0.99 to 3.80, P =.05).
Conclusions: RBPu may serve as a surrogate marker for graft dysfunction early after transplantation for patients with normal graft function, allowing early institution of intervention therapies to prolong allograft survival.