Biomarkers in IgAN: Why Hematuria and GFR Slope Matter

This episode, "Biomarkers in IgAN: Why Hematuria and GFR Slope Matter," features the panel scrutinizing the tools they rely on.

Dr. Rovin catalogs the biomarkers currently in use: proteinuria, albuminuria, GFR, and hematuria. He calls proteinuria flawed because it represents many different processes, yet still targets its reduction. He notes he increasingly measures albuminuria alongside proteinuria and expects the two to correlate. Dr. Rovin argues the community lacks a good handle on GFR, since estimating equations are imprecise. He describes excitement about a transdermal system that measures GFR in real time and correlates with iothalamate. Dr. Rovin says he follows hematuria seriously, examining the urine sediment under the microscope for glomerular bleeding. He explains he uses these markers serially to judge whether treatment is working. Dr. Rovin voices the shared wish for something specific, an equivalent of the PLA2R antibody in membranous disease. He cautions that galactose-deficient IgA1 is not that marker, since healthy people carry it too. He suggests specific pathogenic isoforms or autoantibodies against it may prove more useful in the future. Dr. Mehdi addresses GFR slope, calling it easier said than done given estimating-equation error. He notes 25% to 30% of patients have a true GFR well above or below the estimate. He tells trainees the field follows biomarkers of kidney damage, not biomarkers of IgA nephropathy itself. Dr. Fervenza then names the elephant in the room, hematuria. He argues that a proteinuria-centric view blinds nephrologists to a defining feature of glomerulonephritis. He contrasts two patients with equal proteinuria but opposite hematuria, insisting they are not the same. Dr. Parikh agrees fully, noting hematuria is often overlooked because it does not anchor trial endpoints, and welcomes newer trials reporting hematuria data.

The next episode in this series, "2025 KDIGO Updates in IgAN: Dual Pathways and New Targets," shifts to Dr. Mehdi on the 2025 KDIGO updates reshaping how the field treats IgA nephropathy.