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 m²/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; β = –0.240, P = 0.004) during follow up, minimal (β = –0.393, P < 0.001) and non‐response (β = –0.403, P < 0.001) were significant predictors. In further investigation of complete and partial response groups, MAP (β = –0.332, P = 0.001) and relapse of proteinuria (β = –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.