Predictors for progression in immunoglobulin A nephropathy with significant proteinuria.

Aim: Proteinuria is a primary factor requiring treatment in immunoglobulin (Ig)A nephropathy. The purpose of this study was to assess the relevance of treatment response and relapse of proteinuria with renal function decline.

Methods: One hundred and twenty-five biopsy-proven primary IgA nephropathy patients who had more than 1.0 g/day proteinuria at the first assessment were studied. All patients underwent anti-proteinuric treatment, and the association of the rate of renal function decline with treatment responsiveness, clinical and laboratory data was investigated.

Results: The treatment response of the patients was: 30.4% complete response (<0.3 g/day proteinuria), 32.8% partial response (0.3-1.0 g/day), 23.2% minimal response (decrement but not reduced to <1 g/day) and 13.6% no response (no decrement of proteinuria). The slope of renal function decline (-1.06 vs-1.24 mL/min per 1.73 m(2)/year, P = 0.580) was comparable between complete and partial response groups, but they were slower than those of minimal or non-response groups (P < 0.001). In multivariate analysis including other parameters, mean arterial pressure (MAP; beta = -0.240, P = 0.004) during follow up, minimal (beta = -0.393, P < 0.001) and non-response (beta = -0.403, P < 0.001) were significant predictors. In further investigation of complete and partial response groups, MAP (beta = -0.332, P = 0.001) and relapse of proteinuria (beta = -0.329, P = 0.001) were independently associated with slope of renal decline.

Conclusion: Achievement of less than 1.0 g/day proteinuria and MAP were important for limiting the loss of renal function, and relapse of proteinuria should be closely monitored in proteinuric IgA nephropathy.