Hematuria in IgA Nephropathy: Marker, Mediator, or Both?

Hematuria is one of the most characteristic clinical manifestations of IgA nephropathy (IgAN), yet its prognostic significance has remained controversial for decades. In this issue, Tang and colleagues provide important new evidence supporting the clinical relevance of persistent hematuria by applying marginal structural models (MSMs) to a large longitudinal cohort of 1,771 patients with biopsy-proven IgAN [1]. Their study demonstrates that while baseline hematuria was not associated with kidney disease progression, sustained time-updated hematuria of ≥100 RBC/μL was independently associated with a significantly increased risk of a composite kidney outcome.