biostudies-literatureShimizu AThe Japan Agency for Medical Research and Development498-506https://www.ebi.ac.uk/biostudies/studies/S-EPMC12950100biostudies-literatureUnknown30(3)<h4>Background</h4>Although proteinuria is a key prognostic marker in immunoglobulin A nephropathy (IgAN), the optimal post-biopsy timing for its assessment remains uncertain, particularly given variability in treatment type and timing. Using longitudinal data from the Japan IgA Nephropathy Prospective Cohort Study (J-IGACS), we sought to identify the post-biopsy time point at which proteinuria most reliably predicts kidney outcomes.<h4>Methods</h4>Proteinuria was assessed at baseline and at 6, 12, 18, and 24 months after biopsy. The primary outcome was defined as a ≥ 50% increase in serum creatinine or initiation of kidney replacement therapy in adults (≥ 20 years) and as a ≥ 25% decline in eGFR or initiation of kidney replacement therapy in patients aged < 20 years. Model performance wasClinical and experimental nephrologyPost-biopsy proteinuria as a universal prognostic marker across diverse clinical courses in IgA nephropathy.PMC12950100JP19ek0109261Tomino YMiura KIto TKikuchi MYokoo THonma SJoh KJ-IGACS working groupMiyazaki YSasaki TIchikawa DKawamura TKatafuchi RHashiguchi ASuzuki HShirai SShibata TShimizu ASuzuki YYasuda TTakahashi KUeda HNishikawa MNakatani SYasuda YHataya HAoki RFujimoto SHirano KSanada SMatsuzaki KMuta KFukao YNihei YOkabe MMoriyama TNakanishi KFukuda ASakaguchi RShima YKihara MTsuboi NYokote SNishino TKoike KUrushihara MfalsePost-biopsy proteinuria as a universal prognostic marker across diverse clinical courses in IgA nephropathy.<h4>Background</h4>Although proteinuria is a key prognostic marker in immunoglobulin A nephropathy (IgAN), the optimal post-biopsy timing for its assessment remains uncertain, particularly given variability in treatment type and timing. Using longitudinal data from the Japan IgA Nephropathy Prospective Cohort Study (J-IGACS), we sought to identify the post-biopsy time point at which proteinuria most reliably predicts kidney outcomes.<h4>Methods</h4>Proteinuria was assessed at baseline and at 6, 12, 18, and 24 months after biopsy. The primary outcome was defined as a ≥ 50% increase in serum creatinine or initiation of kidney replacement therapy in adults (≥ 20 years) and as a ≥ 25% decline in eGFR or initiation of kidney replacement therapy in patients aged < 20 years. Model performance was2026-01-01T00:00:00Z2026 Mar2026-07-17T01:11:02.124Z2026-07-12T03:13:07.69ZS-EPMC129501004163694010.1007/s10157-025-02808-3