When to Biopsy in IgAN: Presentation, Thresholds, and Monitoring

"When to Biopsy in IgAN: Presentation, Thresholds, and Monitoring" takes up the question of which patients warrant a diagnostic biopsy.

Dr. Mehdi identifies the most common presentation he sees: microscopic hematuria with proteinuria in patients who have seen multiple providers. He notes RPGN is rare, and that by the time patients reach specialists they often already show glomerulosclerosis and fibrosis. Dr. Parikh raises new-onset hypertension in young patients as another important trigger to look for hematuria. He asks the panel to describe their thresholds for proceeding to biopsy versus monitoring. Dr. Mehdi explains that thresholds have dropped over the past five to ten years. He cites evidence that even timed proteinuria of 0.5 grams predicts lifetime progression. The population he still struggles with is preserved GFR, microscopic hematuria, and under 0.5 grams of proteinuria. Dr. Fervenza agrees and offers a concrete Mayo approach using measured creatinine and iothalamate clearance. He describes a normotensive 23-year-old with 600 milligrams of proteinuria and a clearance of 108, whom he would not rush to biopsy. For that patient he considers genetic testing for collagen IV nephropathy instead. But an identical patient with a clearance of 80 goes to biopsy, because that value is abnormal at 23. Dr. Fervenza stresses that deferring biopsy is not discharge; such patients need follow-up every four months. Dr. Rovin describes his low threshold, noting biopsies of patients with only glomerular bleeding reveal unexpected histologic lesions. He emphasizes seeing patients regularly rather than annually, using urinalysis and sediment to catch red or white blood cell casts. Dr. Parikh frames this as a paradigm shift from infrequent follow-up toward close monitoring and genetic testing, while noting collagen IV mutations can overlap with IgA nephropathy.

In "IgAN Biopsy Interpretation: Beyond the Oxford Classification," the panel will debate whether the Oxford classification still guides prognosis and treatment, with Dr. Rovin opening a familiar can of worms.