Abstract:

Objective To evaluate the role of complement （C）1q determination for autoimmune diseases（AID）. Methods A total of 203 AID patients [86 cases of autoimmune thyroid disease（AITD）,56 cases of systemic lupus erythematosus（SLE）,32 cases of rheumatoid arthritis（RA）and 29 cases of other connective tissue diseases] and 100 healthy subjects（healthy control group）were enrolled from the Second Affiliated Hospital of Nanchang University from May 2014 to September 2015. Using transmission turbidimetry,turbidimetric immunoassay,indirect immunofluorescence（IIF）and linear immunoblot assay（LIA）,C1q, C-reactive protein（CRP）,antinuclear antibody（ANA）,anti-double-stranded DNA（ds-DNA）antibody and anti-Sm antibody were determined respectively. Results Compared with healthy control group, C1q level in SLE group was decreased（P<0.05）,and that in RA group was increased（P<0.05）. The level of C1q decreased with the increasing of ANA titer degrees（P<0.05）. The C1q levels in anti-ds-DNA antibody positive and anti-Sm antibody positive group were lower than those in anti-ds-DNA antibody negative and anti-Sm antibody negative group （P<0.05）. CRP levels in AID groups were increased（P<0.01）. The correlation coefficient between C1q and CRP was >0.300（P<0.05）. Regression equation showed that the range of cut-off values（COV）was 167.42-198.37 mg/L. For C1q and autoantibodies,the abnormal rate（C1q<COV）was higher in ANA positive group than that in ANA negative group,that in ANA positive with anti-ds-DNA positive group was higher than those of other autoantibody distribution types,and that in ANA positive with anti-Sm antibody positive or with anti-Sm and anti-ds-DNA antibodies positive increased. The abnormal rate（C1q>COV）in ANA negative group was 67.2%. Conclusions For patients with AID,C1q has moderate correlation with CRP,the abnormal rate of C1q has correlations with some autoantibody distribution types and the status of patients' illness.

Key words: Complement 1q, Autoantibodies, Autoimmune diseases, Systemic lupus erythematosus