Clinical validation of immunoglobulin A nephropathy diagnosis in Swedish biopsy registers

Aims: The aims of this study were to validate the diagnosis of IgA nephropathy (IgAN) in Swedish biopsy registers against patient charts and to describe the clinical characteristics of patients with a biopsy indicating IgAN. Methods: This is a population-based cohort study. Out of 4,069 individuals with a renal biopsy consistent with IgAN (biopsies performed in 1974–2011), this study reviewed patient charts of a random subset of 127 individuals. Clinical and biopsy characteristics at the time of biopsy were evaluated, and positive predictive values (PPV) were calculated with 95% confidence intervals (CI). Results: Out of 127 individuals with a renal biopsy consistent with IgAN, 121 had a likely or confirmed clinical diagnosis of IgAN, primary or secondary to Henoch–Schönlein purpura, yielding a PPV of 95% (95% CI =92%–99%). The median age at biopsy was 39 years (range: 4–79 years); seven patients (6%) were Conclusion: A histologic diagnosis of IgAN has a high PPV for a diagnosis of IgAN confirmed by review of patient charts. Keywords: general population-based, histopathology, IgA nephropathy, kidney, renal disease, validation studies Corrigendum for this paper has been published