Evaluation of serum C1Q and anti-C1Q levels in patients with systemic lupus erythematosus and their relationship with disease parameters

Purpose: In this study, it was aimed to determine C1q and anti-C1q levels in SLE patients and to evaluate their relationship with disease parameters. Methods: The study group consisted of 60 patients who were followed up with the diagnosis of SLE in the Aydın Adnan Menderes University Medical Faculty Practice and Research Hospital Rheumatology Polyclinic between January 2022 and July 2022. After obtaining the written and verbal consents of the patients, the case report form was filled by us; age, gender, disease duration, comorbid diseases and additional rheumatological disease, at the time of diagnosis and throughout the disease; fever, photosensitivity, malar rash, oral ulcer, hematological involvement, renal involvement, CNS involvement, serositis, arthritis, vasculitis, aseptic necrosis, Raynaud phenomenon, myositis findings were recorded. As laboratory findings; ANA, ANA profile, RF, anti-CCP, C3, C4, direct coombs, ACA IgM, ACA IgG, lupus anticoagulant, anti Beta 2 glycoprotein, 24-hour urine protein, complete urinalysis, ESH, CRP, albumin results, file information analyzed and recorded. Disease activity was evaluated according to the SLEDAI score. ELISA method was used to determine C1q and anti-C1q levels. Statistical analyzes were recorded in SPSS 20.0. P<0.05 was considered statistically significant. Results: Of the 60 SLE patients included in the study, 95% were women, and the mean age was 40.9 years. The mean duration of the disease was 119.8 months. Low C1q was detected in 36 (60%) patients and anti-C1q positivity was found in 3 (5%) patients, and the mean anti-C1q level was 109.4±26.8 μg/ml. In 9 (60%) of 15 patients with photosensitivity, 5 (71.4%) of 7 patients with alopecia, 7 (63.6%) of 11 patients with arthritis, 15 (65%, 65%) of 23 patients with renal involvement, 8 (88.9%) of 9 patients with hematological involvement had low C1q. When the laboratory findings were compared with the C1q level, 4 (66.7%) of 6 patients with direct coombs positivity, 8 (57.1%) of 14 patients with anemia, half of 4 patients with thrombocytopenia, 10 (52, 5%) of 19 patients with hypocomplementemia, in all 3 patients with ACA IgG positivity, half of the 4 patients with positive lupus anticoagulant, and 6 (66.7%) of 9 patients with proteinuria >500mg/day had low C1q. While the mean anti-C1q level was 114.8±25.1 in patients with C1q deficiency, it was 101.4±27.9 μg/ml in patients without C1q deficiency (p:0.058). LN was present in 15 (41.7%) of 36 patients with C1q deficiency (p>0.05). When the mean anti C1q level was compared with the clinical findings, a significant correlation was found with Raynaud's phenomenon. When the mean anti C1q level was compared with the laboratory findings, no statistically significant correlation was found. When the correlation between the anti-C1q level of the patients and the SLEDAI score, the amount of proteinuria, ESR and CRP level was evaluated, there was no significant correlation between the parameters according to the Spearman's correlation analysis. Conclusion: Patients with C1q deficiency have more severe disease findings, and patients with high anti-C1q levels have a higher ratio of disease-specific clinical findings. C1q and anti-C1q level measurements are useful in the diagnosis and follow-up of SLE.