Associations of different assays for antibodies to C1q (anti-C1q) and to dsDNA (anti-dsDNA) and of complements C3 and C4 with disease activity in patients with systemic lupus erythematosus (SLE) were studied. The clinical manifestations of 223 SLE patients were recorded, and the disease activity was assessed by the SLEDAI score. Anti-C1q were determined by two enzyme-linked immunosorbent assays (ELISA) and anti-dsDNA by a radioimmunoassay (RIA), a Crithidia immunofluorescence (IF) assay and three ELISA assays using human telomere DNA, plasmid DNA circles, or calf thymus DNA as antigens, respectively. Complement C3 and C4 were determined by nephelometry. Control sera were obtained from 98 blood donors. In patients with SLE, the prevalence of anti-C1q was 17-18% and that of anti-dsDNA was 36-69%. Anti-C1q, anti-dsDNA, and complement C3 and C4 correlated well with the overall activity of SLE (r = 0.323-0.351, 0.353-0.566, and -0.372-0.444, respectively; P < 0.001). Sensitivity, specificity, positive predictive value, and negative predictive value for active lupus nephritis among SLE patients were 40-44, 92, 29, and 91-92% for anti-C1q and 48-68, 29-66, 11-16, and 86-91% for anti-dsDNA, respectively. Patients with active nephritis had higher levels of anti-C1q and lower levels of C3 and C4 than patients with inactive nephritis (P = 0.003-0.018). The corresponding associations of anti-dsDNA were somewhat weaker (P = 0.023-0.198). Hematological parameters reflecting disease activity correlated clearly better with anti-dsDNA and complement C3 and C4 than with anti-C1q. Anti-C1q is inferior to anti-dsDNA as a diagnostic test in SLE and in the evaluation of overall clinical activity of the disease. Anti-C1q together with complement C3 and C4 may offer useful additional information to monitor lupus nephritis activity. There are no practical differences between different assays for anti-C1q and anti-dsDNA.

When compared to population controls women with SLE are normally fertile, use less OCs and more IUDs, have earlier menopause and use HRT as frequently. Family size is reduced, especially in lupus nephritis patients, and pregnancy-associated complications are more common.

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The aim was to study the association of smoking with the activity and severity of systemic lupus erythematosus (SLE) and the production of antibodies to dsDNA. The study included 223 SLE patients attending the outpatient clinics at Helsinki University Central Hospital. The history of smoking was obtained by personal interview, and clinical data related to SLE by interview, clinical examination and chart review. The activity of SLE was assessed by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score and permanent damage by the SLICC/ACR score. Antibodies to dsDNA were determined by three ELISA assays, by the indirect immunofluorescence technique using Crithidia luciliae cells as substrates and by the Farr assay. There were no significant differences in the SLEDAI scores between current smokers (73 patients), ex-smokers (59) and never-smokers (91), though current smokers tended to have lower disease activity. The SLICC/ACR scores between the groups were practically equal. Current smokers had significantly lower levels of antibodies to dsDNA than ex- and never-smokers (p = 0.025). Our study suggests that cigarette smoke may have immunosuppressive effect on autoantibody production in patients with SLE. Permanent damage was not found to be associated with smoking.