A multi-center cohort study evaluated hemoglobinuria as a marker of inflammation in IgA nephropathy

Area of Science:

• Nephrology
• Immunology
• Pathology

Background:

• Hematuria is a key indicator of glomerular inflammation in IgA nephropathy (IgAN).
• Current IgAN risk assessment relies on proteinuria and eGFR, with limited characterization of urinary findings' link to histology.
• The association between urinary findings and specific histological lesions in IgAN requires further elucidation.

Purpose of the Study:

• To investigate the association between urinary findings (hemoglobinuria, hematuria, proteinuria) and histological lesions in IgA nephropathy (IgAN).
• To evaluate the utility of dipstick hemoglobinuria as a marker for active disease in IgAN.
• To compare the predictive value of different urinary markers for specific Oxford Classification MEST-C components.

Main Methods:

• Multicenter retrospective cohort study of 441 patients with biopsy-proven IgAN and concurrent urinalysis.
• Logistic regression and random-effects meta-analysis were used to assess associations between urinary findings and MEST-C components.
• Analysis focused on individual MEST-C components and composite inflammatory lesions (M1, E1, C1/C2).

Main Results:

• Hemoglobinuria was significantly associated with active inflammatory lesions (M1, E1, crescentic lesions) in IgAN.
• Hematuria also correlated with M1, E1, and C1/C2 lesions, indicating active glomerular inflammation.
• Proteinuria was primarily associated with chronic tubulointerstitial lesions (T1/T2), while hemoglobinuria and hematuria did not correlate with chronic changes.

Conclusions:

• Dipstick hemoglobinuria serves as a valuable indicator of active histological disease in IgA nephropathy.
• Hemoglobinuria may complement existing biomarkers for assessing IgAN disease activity.
• Urinary findings, particularly hemoglobinuria, provide clinically relevant information for IgAN patient management.