Proteinuria, Estimated Glomerular Filtration Rate and Urinary Retinol-Binding Protein as Clinical Predictors of Long-Term Allograft Outcomes in Transplant Glomerulopathy

Background/Aims: We aimed to explore the associations between clinical parameters and long-term allograft outcomes in transplant glomerulopathy (TG) in a large retrospective cohort with long follow-up. Methods: Clinical and laboratory data at biopsy from 180 cases of TG with an estimated glomerular filtration rate (eGFR)> 15ml/min/1.73m² from January 2004 to December 2016 at our center were retrospectively analyzed. The main outcome of this study was initiation of replacement therapy or an eGFR declined to < 15 ml/min/1.73m². Results: During a median follow-up of 5 years (interquartile range 2.6-8.2 years), 117 cases (65.0%) achieved the combined event. Kaplan-Meier method yielded the 1-year and 5-year cumulative renal allograft survival rates after a histopathologic diagnosis of TG were 84% (95% confidence interval [CI] 81-87%) and 33% (95% CI 27–39%) respectively. In univariate analysis, allograft outcome differed significantly by eGFR, proteinuria, blood hemoglobin level, urinary retinol-binding protein (urRBP) and urinary N-acetyl-β-D-glucosaminidase (urNAG) level at the time of biopsy. Multivariate Cox analysis revealed that a higher level of eGFR was the most powerful predictor of allograft survival. Compared with those with eGFR≥60, the hazard ratio (HR) increased from 4.50 (95% CI: 1.03-19.71, p=0.0462) for patients with eGFR between 30 and 59 ml/min/1.73m² to 9.14 (95% CI 1.97-42.45, P=0.0047) when eGFR decreased to 15 to 29 ml/min/1.73m². Additionally, proteinuria and higher urRBP values (≥2.85mg/dl) were found to confer much worse survival rates for TG patients in multivariate Cox analysis. Male sex (HR 0.48, P=0.02) and HCV infection (HR 1.78, P=0.0499) were also found to be independent risk factors for worse allograft survival. Conclusion: Five clinical features—impaired renal function, higher proteinuria, higher urRBP level, male sex and HCV infection—are independent predictors of an unfavorable renal allograft outcome. urRBP is a simple and useful parameter that can add invaluable information for the clinical follow-up of patients with TG.