Proteinuria during Follow-Up Period and Long-Term Renal Survival of Childhood IgA Nephropathy

BACKGROUND: Proteinuria is the most important risk factor for IgA nephropathy progression. The purpose of this study is to evaluate the long-term outcome and risk factors for poor prognosis in childhood IgA nephropathy. METHODS: Patients who were diagnosed with IgA nephropathy between 1972 and 1992 at the Tokyo Metropolitan Kiyose Children’s Hospital were included. We analyzed risk factors for progression to end-stage kidney disease (ESKD) and chronic renal insufficiency (CRI) using Kaplan-Meier method and multivariate analyses of Cox proportional hazard model. RESULTS: One hundred patients were included and the median observation period was 11.8 years. Twelve and 17 patients progressed to ESKD and CRI, respectively. The survival probabilities were 90.0% at 10 years and 79.8% at 20 years for ESKD, and 86.1% at 10 years and 72.3% at 20 years for CRI. Notably, patients with heavy proteinuria with hypoalbuminemia during follow-up period showed extremely poor prognosis. In this group, the survival rate at 10 years from ESKD and CRI was 40.6% and 20.8%, respectively. By multivariate analysis, proteinuria at diagnosis and proteinuria during follow-up period were risk factors for ESKD, whereas glomeruli showing mesangial proliferation ≥50% and proteinuria during follow-up period were risk factors for CRI. Patients without heavy proteinuria during follow-up period did not develop CRI and 63% of patients with mild proteinuria during follow-up period showed no proteinuria at the last observation. CONCLUSIONS: The degree of proteinuria during follow-up period is the strongest risk factor for ESKD and CRI.