Prediction in idiopathic membranous nephropathy.

BACKGROUND: Results of the prognosis of idiopathic membranous nephropathy are conflictive and prevent an effective risk stratification. These conflicts are explained in part by insufficient consideration of methodological principles for prognostic research. This cohort study is aimed at identifying clinical predictors for risk stratification while paying particular attention to methodology.

METHODS: We studied 120 patients with idiopathic membranous nephropathy. Baseline data were extracted at the time of diagnostic renal biopsy, and patients were followed prospectively. Predictors were identified for the end points end-stage renal failure (ESRF) and ESRF or death.

RESULTS: From the 120 patients followed for a median of five years (1 to 24 years), 19% developed end-stage renal failure or deterioration of renal function. Proteinuria of more than 3.5 g/day persisted in 34%, and 47% were in complete or partial remission. The Kaplan-Meier estimated probability of renal survival was 91 +/- 3% at five years and 75 +/- 6% at ten years. The predictors for the primary outcome, ESRF, identified in a Cox proportional hazards model, were histological stage (Ehrenreich-Churg) III-IV (hazard ratio 5.3, CI 1.9 to 15.0, P = 0.002) and nephrotic syndrome (hazard ratio 7.9, CI 1.1 to 61.5, P = 0.04); the predictors for the secondary outcome, ESRF or patient death, were histological stage III-IV (hazard ratio 2.8, CI 1.3 to 6.0, P = 0.008), nephrotic syndrome (hazard ratio 3.0, CI 1.1 to 8.0, P = 0.003) and comorbidity (hazard ratio 2.8, CI 1.3 to 5.9, P = 0.007). Nephrotic syndrome and histological stage III-IV allowed the demarcation of the high-risk group from the remaining patients (P < 0.0001).

CONCLUSION: Histological stage, nephrotic syndrome, and comorbidity predict end-stage renal failure or death in idiopathic membranous nephropathy. Identification of the high-risk group at the time of diagnostic renal biopsy will permit appropriate treatment to be targeted to the patients who might benefit the most from the therapy in future clinical trials.