Glomerulonephritis (GN) mostly occurs as a result of dysregulated immune system. In GN patients the impairment of the immune mechanisms can be primary or secondary to an underlying autoimmune disease (AID). Antinuclear antibodies (ANA) are hallmark of AID. ANA may be found nonspecifically in certain infections, malignancies and also in 5%-10% healthy individuals at low titers. In AID ANA are usually found at high titer (≥ 1: 160). A positive ANA test with high titer is followed by anti-double stranded deoxyribonucleic acid (anti-dsDNA) and anti-extractable nuclear antigens (anti-ENA) tests for characterization of underlying AID. Heavy proteinuria can affect ANA results, however available data based on this information is scarce.
Our aim was to determine the impact of heavy proteinuria on ANA titer, anti-dsDNA and anti-ENA in GN patients.
Over all 150 GN patients were enrolled in this study with a positive ANA test. Serum samples of these patients were further tested for anti-dsDNA and anti-ENA. ANA titer of 1:160 was taken as significant. Proteinuria was assessed by spot protein/creatinine ratio. A ratio of ≥1 was considered as heavy proteinuria (equivalent to 1gm protein/day). Data was analyzed using SPSS software version. 20
Of total, heavy proteinuria was present in 119(79%) patients. Overall low ANA titers (≤1:80) were present in 37(25%) patients. Of 33 patients with heavy proteinuria and low ANA titers, ANA was characterized in 11 patients. These include anti-dsDNA (two), anti-SSA (four), anti-Sm (one), anti-histones (one), anti-RNP (two), anti-Pm-Scl (one) and anti-ribosomal P protein (two). There was no significant difference in the prevalence of various autoantibodies in patients with high or low ANA titers with heavy proteinuria.
This study highlights the importance of low ANA titer in GN patients especially in the presence of heavy proteinuria. This group of patients needs special attention in terms of autoantibodies titer assessment. In this scenario ANA should be characterized via specific autoantibodies and clinically correlated for the evaluation of underlying autoimmune disorder in order to provide better patient management.