Respective predictive role of urinary albumin excretion and nonalbumin proteinuria on graft loss and death in renal transplant recipients

Abstract

Proteinuria is constituted by urinary albumin (UAE) and nonalbumin proteins (NAP). UAE was shown to predict ESRD and death. Whether NAP predicts graft or patient outcome is unknown in renal transplantation. We retrospectively analyzed the impact of UAE and NAP respectively on end-stage renal disease (ESRD) and death in 616 renal transplant recipients. In subjects with proteinuria <0.25 g/day, 76% of urine proteins were NAP; in those with >1 g/day, 44% of the urine proteins were NAP. Determinants of UAE and NAP were partly different: fasting glucose, body weight, donor cause of death and cyclosporine were significantly associated with NAP (but not UAE); panel reactive antibodies (PRA) and rapamycine were significantly associated with UAE (but not with NAP). NAP expressed as a continuous (HR: per g/day: 4.00 [2.85-5.63], p < 0.0001) or a categorical (presence vs. absence, HR = 29.09[8.80-96.20], p < 0.0001) parameter and UAE (per g/day, HR = 1.86 [1.24-2.78], p < 0.0001) were risk factors for graft loss in univariate analyses. NAP remained significant even after adjustment on UAE. The presence of NAP (HR: 5.37 [2.55-11.34], p < 0.0001) and macroalbuminuria (HR: 4.12 [1.65-10.29], p = 0.0024) were risk factors for death. Proteinuria is made of various proportions of UAE and NAP in renal transplantation; these two parameters provide different information on graft/patient survival.