Clinical significance of anti-C1q antibodies in SLE

Abstract

Abstract Lupus nephritis (LN) is a severe and frequent complication of systemic lupus erythematosus (SLE). Untreated cases very often lead to patients’ death; therefore, it is important to use markers sensitive and specific enough for the diagnosis and subsequent monitoring of nephritis. Autoantibodies against double-stranded DNA (anti-dsDNA) are believed to play a major role in SLE in general and so their significance in prediction and monitoring of glomerular inflammation is low. For prediction of renal flares and effective, well-timed therapy, it is required to have an appropriate marker available. In our study, we have tested sera of 85 SLE patients with or without LN. The criterion for LN determination was the degree of proteinuria (persistent proteinuria > 0.5 g/day, according to ACR criteria for LN). Disease activity was described by SLE disease index (SLEDAI) score, renal functions were stated according to British Isles Lupus Assessment Group score. There were anti-C1q, total anti-dsDNA and high-avidity anti-dsDNA detected in the patients’ sera. We did not find any significant difference in average SLEDAI value between patients with renal and non-renal organ complications. Positivity of anti-C1q was more frequent in patients with nephritis than in those without any history of renal disease (58.3 vs. 39.1%). Higher prevalence of these antibodies was evident in patients with clinically active LN than in those without renal improvement (73.1 vs. 39.1%). When comparing anti-C1q with antibodies against structures of DNA, significant differences were found in case of high avidity anti-dsDNA. Our results have confirmed the studies showing that anti-C1q antibodies could serve as a reliable serological marker of LN activity along with other laboratory tests. Detection of anti-C1q together with high avidity anti-dsDNA antibodies seems to be a good algorithm for the prediction of possible renal flares in SLE patients.