IgAN Biopsy Interpretation: Beyond the Oxford Classification

In "IgAN Biopsy Interpretation: Beyond the Oxford Classification," our experts turn to how much a pathology score should drive decisions.

Dr. Parikh asks the panel to weigh the relevance of the Oxford classification for prognosis and treatment. Dr. Rovin argues it needs revision and warns it can make nephrologists lazy. He explains that an E lesion may involve one tuft or every tuft, yet the score forces a yes-or-no cutoff. Nothing in nephrology, he says, is truly black or white, so he insists on reading the biopsy himself. The panel notes KDIGO already advises against using MEST-C to decide therapy. They stress that since a biopsy is invasive, clinicians should extract maximum histologic and molecular information. Dr. Fervenza adds that the classification rests on percentage cutoffs, so scoring zero does not mean no inflammation. He cautions that biopsy is hit-or-miss and that disease may live in the interstitium, not just the glomeruli. He warns clinicians can miss superimposed acute interstitial nephritis if they only read the MEST score. Dr. Mehdi finds value in the individual lesions beyond the score. He explains that mesangial expansion signals immune activation and endocapillary changes signal inflammation. Dr. Fervenza reframes the practical question as simply whether the biopsy shows inflammation. Dr. Rovin agrees but notes defining inflammation in IgA nephropathy is harder than in lupus. He urges nephrologists to call the pathologist and review slides even when biopsies are sent out. Dr. Rovin also cautions that biopsy quality matters, since eight glomeruli may not represent the tissue. He clarifies that Oxford is step one in an evolving classification, citing CD68 staining to judge whether S lesions are active. The panel concludes it is time to update the Oxford classification.

Up next, in "Biomarkers in IgAN: Why Hematuria and GFR Slope Matter," the experts examine which biomarkers actually track IgA nephropathy activity, and why the perfect one does not yet exist.