Authors of a post hoc analysis of the prospective Japan IgA Nephropathy Prospective Cohort Study evaluated proteinuria at diagnosis and every 6 months through 24 months in 588 patients with biopsy-confirmed IgA nephropathy (IgAN). During a median 78-month follow-up, proteinuria measured at 18 months showed the strongest association with long-term kidney outcomes and the best discriminatory performance of all time points assessed. An 18-month proteinuria threshold of 0.44 g/day or g/gCr provided 79% sensitivity and 81% specificity. Patients at or above this level had a substantially higher risk of the composite kidney outcome than those below it.
The findings suggest that longitudinal proteinuria monitoring, specifically the 18-month measurement, may add meaningful prognostic information beyond the level recorded at diagnosis. The association was consistent across different initial treatment groups, supporting the potential value of a time-based proteinuria target during follow-up. However, the analysis excluded patients with early events or incomplete longitudinal data, used both g/day and g/gCr measurements, included relatively few outcome events, and was conducted in a Japanese cohort, so the proposed less than 0.44 threshold requires validation before it can be considered a universal treatment target.
Reference: Shimizu A, Tsuboi N, Ueda H, et al. Post-biopsy proteinuria as a universal prognostic marker across diverse clinical courses in IgA nephropathy. Clin Exp Nephrol. 2026 Mar;30(3):498-506. doi: 10.1007/s10157-025-02808-3.
