Hematuria is one of the defining clinical features of IgA nephropathy (IgAN), yet contemporary risk assessment remains largely centered on proteinuria and eGFR. Vargas-Brochero and colleagues asked an important question: can the simple presence of blood on urinalysis provide information about ongoing glomerular inflammation?
In this multicenter retrospective study, investigators evaluated 441 patients with biopsy-proven IgAN from four international cohorts between 2015 and 2025. Urinary hemoglobin by dipstick, microscopic hematuria, and proteinuria obtained around the time of biopsy were compared with individual components of the Oxford MEST-C classification.
The findings were striking. Dipstick hemoglobinuria was associated with active inflammatory lesions, including mesangial hypercellularity (M1; OR 1.77), endocapillary hypercellularity (E1; OR 1.75), and crescents (C1/C2; OR 1.57). Microscopic hematuria showed similar, although generally weaker, associations. For the composite of M1, E1, and/or C1/C2 lesions, hemoglobinuria demonstrated the strongest association (OR 2.28), compared with microscopic hematuria (OR 1.36) and proteinuria (OR 1.20).
Importantly, hemoglobinuria and microscopic hematuria were not associated with chronic histologic damage, whereas proteinuria correlated with tubular atrophy/interstitial fibrosis (T1/T2). This distinction suggests that these urinary biomarkers may be capturing different aspects of IgAN biology: hematuria reflecting active glomerular inflammation and proteinuria reflecting, at least partly, accumulated structural injury.
The clinical takeaway is refreshingly simple: don’t ignore the blood on the dipstick. In an era increasingly focused on disease activity and targeted therapies in IgAN, inexpensive and readily available hemoglobinuria may provide complementary information beyond proteinuria and eGFR when assessing ongoing disease activity.
