We previously employed ELISA-based assays to determine serum concentrations of total IgA, IgG, Gd-IgA1, Gd-IgA1-specific IgA, and Gd-IgA1-specific IgG in cohorts that included 135 patients with biopsy-proven IgAN, 79 patients with other biopsy-proven chronic kidney diseases (CKD), and 106 healthy controls (HC).[16] Follow-up analysis of the CKD patients identified three individuals with evidence of renal IgA1 deposits and these three individuals were therefore excluded from this study. Here, IGHA1 is linked to chronic kidney disease.