title: Anti-C1q antibody as a marker of disease activity in systemic lupus erythematosus.
abstract: The present study was conducted to examine the usefulness of anti-C1q antibody as a marker of disease activity in Indian patients with systemic lupus erythematosus (SLE). We standardized the assay for detection of IgG anti-C1q antibody using ELISA. The normal cut-off level was determined by testing 57 healthy, age and sex matched controls to be 53 units/m1 (mean +/- 2 SD). Patients with SEL (97 females and 13 males) were studied and the following parameters were obtained on all: SLE disease activity index (SLEDAI), anti-C1q, anti-ds DNA and C3. Correlations were tested between these parameters using Spearman's rank correlation coefficients. Anti-C1q was found positive in 66 (60%) patients while anti-ds DNA was found in 78 (71%). The positive predictive values of anti-C1q and anti-ds DNA for lupus nephritis were 59 and 61 per cent respectively. The titres of anti-C1q correlated positively with SLEDAI (P < 0.01) and anti-ds DNA (P < 0.01) and negatively with C3 levels (P < 0.001). No significant correlation was observed between anti-C1q positivity and any particular organ involvement. Similarly, no correlation was found between anti-C1q and proliferative lupus nephritis. Anti-C1q was found positive in 5 of 9 patients with moderate SLEDAI scores and negative for anti-ds DNA antibody. It is concluded that anti-C1q antibody can serve as a general marker for lupus activity, supplementing the currently used serum markers.
authors.affiliation: Department of Medicine, All India Institute of Medical Sciences, New Delhi.
authors.forename: A
authors.initials: A
authors.lastname: Kumar
authors.forename: R
authors.initials: R
authors.lastname: Gupta
authors.forename: T
authors.initials: T
authors.lastname: Varghese
authors.forename: R M
authors.initials: RM
authors.lastname: Pande
authors.forename: V K
authors.initials: VK
authors.lastname: Singal
authors.forename: O P
authors.initials: OP
authors.lastname: Garg
mesh_terms: D000293:Adolescent; D000328:Adult; D000906:Antibodies / Q000032:analysis*; D000974:Antibodies, Antinuclear / Q000032:analysis; D015415:Biomarkers; D015922:Complement C1q / Q000276:immunology*; D004247:DNA / Q000276:immunology; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged
chemical_list: D000906:Antibodies; D000974:Antibodies, Antinuclear; D015415:Biomarkers; D015922:Complement C1q; D004247:DNA