Abstract:

Objective To investigate the role of anti-chromatin antibody determined by automatic multiplex bead immunoassay in the diagnosis of connective tissue diseases. Methods The expressions of anti-chromatin antibody in 384 patients with connective tissue diseases [243 cases of systemic lupus erythematosus（SLE）,39 cases of polymyositis（PM）,15 cases of mixed connective tissue disease（MCTD）,51 cases of Sjögen's syndrome（SS）,7 cases of systemic sclerosis（SSc） and 29 cases of rheumatoid arthritis（RA）],200 non-rheumatic disease patients（disease control group） and 200 healthy subjects（healthy control group） were determined. Anti-double-stranded DNA（dsDNA） antibodies,anti-histone antibodies and anti-nucleosome antibodies were determined by enzyme-linked immunosorbent assay（ELISA）. Anti-nuclear antibodies（ANA） were determined by indirect immunofluorescence. The correlation between systemic lupus erythematosus disease activity index（SLEDAI） score and anti-chromatin antibody was evaluated. Receiver operating characteristic（ROC） curve was used to analyze the roles of these indicators for the diagnosis of SLE. Results The positive rates of anti-chromatin antibodies in healthy control,disease control,SLE,MCTD,PM,SS,SSc and RA groups were 0.00%,1.00%,70.78%,73.33%,23.08%,17.65%,28.57% and 10.34%,respectively. The positive rate of anti-chromatin antibodies increased with the increase of ANA titer. MCTD,PM,SS,SSc and RA groups were merged into non-SLE group. Serum anti-chromatin antibody level in SLE group was higher than that in non-SLE group（P<0.000 1）. For anti-chromatin antibody,anti-dsDNA antibody,anti-nucleosome antibody and anti-histone antibody in SLE group,the rates of single-antibody positive and the other 3-antibody negative was 45.39%,32.34%,13.42% and 7.37%,respectively. There were some cross-positive rates among the 4 antibodies. The areas under curves（AUC） of anti-nucleosome antibody,anti-chromatin antibody,anti-dsDNA antibody and anti-histone antibody for the diagnosis of SLE were 0.813,0.779,0.777 and 0.613,respectively. There was no correlation between anti-chromatin antibodies and SLEDAI score （r= 0.124 6,P=0.177 0）. There was no statistical significance in serum anti-chromatin antibodies between SLE patients without nephritis and those with nephritis（P>0.05）. Conclusions Automatic multiplex bead immunoassay for the determination of anti-chromatin antibody plays a role in the diagnosis of connective tissue diseases.

Key words: Anti-chromatin antibody, Automatic multiplex bead immunoassay, Connective tissue disease