Background Anti-C1q autoantibodies have been described in patients with systemic lupus erythematosus (SLE) and their presence has been closely correlated with renal disease activity. Serum anti-C1q determination seems to be a valuable non-invasive marker for prediction of renal histopathology in lupus nephritis.
Objectives To assess if anti-C1q and other markers of disease activity are associated with nephritis according to renal BILAG score in a population of patients with SLE.
Methods A sample of portuguese SLE patients was grouped according to BILAG renal score: categories A+ B+ C (active nephritis), category D (inactive nephritis) and category E (no nephritis). Anti-C1q autoantibodies were determined by ELISA (Bühlmann®) with duplicate samples. Levels < 15 units/mL were considered the cut-off for normal sera. Serum ESR, CRP, levels of C3c, C4, CH50, anti-DNAds titres, 25(OH)vitamin D, 24 hour protein excretion and SLEDAI were measured. A multivariate analysis was performed using SPSS 18.0. Adjustments were made for patients´age, disease duration, steroid daily dose (prednisolone equivalents) and hydroxychloroquine daily dose.
Results 160 patients, 148 (92.5%) women, with mean (SD) age of 44.2± 12.59 years, were grouped according to BILAG renal score in categories A+B+C (n=23; 14.4%), category D (n=45; 28.1%) and category E (n=92; 57.5%). All the patients with a history of nephritis (active or previous) had had a biopsy at the time of its diagnosis (n=68; 42.5%). They had mean (SD) disease duration of 12.2± 8.71 years, SLEDAI 3.1± 4.50, SLICC 0.6± 1.07, daily dose of prednisolone 6.5 ± 5.91 mg and of hydroxychloroquine 213.2± 192.76 mg.
An association was found between active renal disease (BILAG score categories A+ B+ C) and higher anti-C1q titres (p<0.01), higher anti-dsDNA titres (p<0.01) and lower C3c levels (p<0.01).
Conclusions In a cohort of portuguese SLE patients, an association was found between anti-C1q titres, C3c levels and anti-dsDNA titres with active nephritis evaluated by BILAG renal scores. These data support the use of anti-C1q as a marker of nephritis presence and activity in SLE.
References Yang XW, Tan Y, Yu F, Zhao MH, Combination of anti-C1q and anti-dsDNA antibodies is associated with higher renal disease activity and predicts renal prognosis of patients with lupus nephritis. Nephrol Dial Transplant. 2012 Sep(9):3552-9. Doi:10.1093/ndt/gfs179.
Chen Z, Wang GS, Wang GH, Li XP, Anti-C1q antibody is a valuable biological marker for prediction of renal pathological characteristics in lupus nephritis. Clin Rheumatol. 2012 Sep;31(9):1323-9. doi: 10.1007/s10067-012-2017-1.
Disclosure of Interest None Declared