[Establishment and application of quantitative detection of serum anti-carbamylated protein autoantibodies by microarray chemiluminescence immunoassay]

Objective To develope a chemiluminescence immunoassay based on microarray protein chip technology for detecting the anti-carbamylated protein (CarP) antibody. We aimed to evaluate the detection performance of this method and to explore its preliminary clinical application value of this index in patients with rheumatoid arthritis (RA). Methods A quantitative detection method for anti-CarP antibody was established to evaluate the precision, minimum detection limit, linear range and specificity of the method. The 95th position of anti-CarP antibody level in serum of 120 healthy controls was defined as the cutoff value. The anti-CarP antibody level and positive rate in RA group and non-RA group were analyzed. And the correlation between anti-CarP antibody and disease activity index in RA group was analyzed. Results The precision of this method for detecting high-level sample and low-level sample was less than 15%; The linear range could reach (3.31~1448.18) AU/mL, and there was almost no cross-reaction between anti-CarP antibody and anti-CCP antibody. Compared with healthy control group, the level of anti-CarP antibody in RA group, anti-CCP antibody positive RA group and joint pain group was significantly higher, and that in undifferentiated connective tissue disease group was also higher. Compared with the 5% positive rate of anti-CarP antibody in healthy control group, the positive rate of RA patients was 28.21%, anti-CCP antibody positive RA patients was 32.2%, joint pain group was 38.89%, which were significantly higher. There was no statistical difference between other disease groups. The level of anti-CarP antibody was weakly correlated with level of rheumatoid factor (RF) and erythrocyte sedimentation rate (ESR) in RA patients, but it was moderately correlated with CRP and IgG level. Conclusion The protein chip chemiluminescence method for quantitative detection of anti-CarP antibody has good detection precision and wide linear range, and has good sensitivity and specificity. Anti-CarP antibody detection is valuable for RA diagnosis and disease activity evaluation.