IGHA1 and nephritis: Circulating galactose-deficient IgA1 (GD-IgA1) was more elevated in IgAV-N patients compared to controls and in IgAV-woN patients (Fig 2A), as previously described [7], and this feature could be used to identify patients with nephritis (AUC = 0.73, CI = 0.56–0.89, p = 0.02; Fig 2B).