Proteinuria:: a new marker of long-term graft and patient survival in kidney transplantation

Background. Proteinuria developing after renal transplantation is associated with increased renal failure. Moreover, proteinuria in the general population has been shown to be associated with morbidity and mortality due to cardiovascular disease, which is the main cause of death in renal transplant patients. The purpose of the present study was to investigate whether persistent proteinuria following renal transplantation was associated with a worse patient and graft survival. Methods. We analysed kidney recipients included in the Spanish Chronic Allograft Nephropathy Study (n = 3365). Proteinuria at 1 year post-transplantation was analysed as a categorical variable (<0.5, 0.5-1, >1 g/day). Results. Post-transplant proteinuria at 1 year was detected in 15.3% of patients. Graft survival in proteinuric patients was significantly lower as compared with patients without proteinuria and the survival was worse with increasing amounts of proteinuria. In the groups with proteinuria, renal graft function at the time of the analysis was worse than in the group without proteinuria. Patient survival was lower in patients with proteinuria although there was no difference between the two groups of proteinuric patients. The main cause of death was vascular disease in all groups of patients but especially in proteinuric patients. The relative risk of graft failure and patient death was higher in proteinuric patients: graft failure [0.5-1 g/day: 2.33 (1.79-3.01, P < 0.0001); >1 g/day: 3.46 (2.73-4.39, P < 0.0001)], patient death [0.5-1 g/day: 2.05 (1.39-3.01, P = 0.0002); >1 g/day: 2.3 (1.55-3.39, P < 0.0001)]. Conclusions. Proteinuria, as in native kidney disease, is an excellent marker of poor long-term allograft prognosis and is an independent risk factor for total and cardiovascular mortality in the renal transplant population.