Serum and urinary galactose-deficient IgA1 as a tool for diagnosis of IgA nephropathy in pediatric patients with hematuria

Background: IgA nephropathy (IgAN) is an immunopathologic diagnosis based on a renal biopsy. Diagnosis of IgAN may not be made in the milder cases or may be delayed until clinical manifestations are severe. We sought to assess the validity of serum and urinary galactose-deficient IgA1(GdIgA1) as a possible non-invasive diagnostic biomarker of IgAN. Methods: A cross-sectional study was conducted at Pediatric Nephrology Clinic, Children's Hospitals, Ain Shams University on 40 patients with recurrent gross glomerular hematuria diagnosed with renal biopsy and divided into two equal groups, group 1 patients with IgAN and group 2 with non-IgA glomerular diseases. Serum and urinary Gd-IgA1 levels were measured by ELISA using an anti-Gd-IgA1 monoclonal antibody (KM55). Laboratory investigations included complete blood count (CBC), erythrocyte sedimentation rate (ESR), complement 3 level in serum (C3), antinuclear antibody (ANA), anti-double strand DNA, urine protein/creatinine (UP/Cr) ratio, serum, and urinary total IgA levels (ELISA). . Results: The study included 20 patients with IgAN, of which 13 were males and 7 were females, in addition to 20 patients with non-IgAN, of which 12 were males and 8 were females. In the IgAN group median age was 6.5 (5-9) years old. In the nonIgAN group, median age was 9 (4.5-13) years old. Serum Gd-IgA1 levels were significantly elevated in children with IgAN compared with children with non-IgA glomerular diseases (p-value 0.001). The serum Gd-IgA1 cutoff point to differentiate between IgAN and non-IgA glomerular diseases was 240 ng/ml with 75 % sensitivity and 80 % specificity and AUC 80.2%. There was no statistically significant difference between IgAN and non-IgA glomerular diseases regarding urinary Gd-IgA1 (p-value 0.08), Ptn/Creat ratio (p-value 0.055), serum and urine total IgA (p-value 0.144 and 0.288). Conclusion: Serum Gd-IgA1 level is higher in IgAN patients compared to non-IgA glomerular diseases, serum Gd-IgA1 may be used as a non-invasive diagnostic biomarker for IgAN patients. .