Association of serum anti-carbamylated protein antibodies with disease activity and bone loss in rheumatoid arthritis

Background We investigated the association of serum anti-carbamylated protein (anti-CarP) antibodies with disease activity and bone loss in rheumatoid arthritis (RA). Methods The serum anti-CarP antibody concentrations of RA and non-RA patients and healthy controls were determined by enzyme-linked immunosorbent assay (ELISA) and then compared. The diagnostic value of anti-CarP antibodies in RA was determined by the receiver operating characteristic curve. Patients with RA and bone erosions were evaluated using ultrasound examinations. Ultrasonography was performed using a semiquantitative scale. The serum receptor activator of nuclear factor Κ-Β ligand (RANKL) concentrations were measured by ELISA to focus on bone loss. Results Peripheral serum anti-CarP antibody concentrations in patients with RA were significantly higher than those in patients without RA and in healthy controls and were positively correlated with disease activity. Anti-CarP antibody concentrations were significantly increased in patients with anti-CCP-positive RA. Positive correlation were found between anti-CarP and RANKL. Increased serum anti-CarP antibodies in women with postmenopausal osteoporosis（OP). Conclusions Anti-CarP antibodies are associated with RA disease activity and may play an important role in bone loss associated with RA. The concentration of anti-CarP antibodies may be beneficial in the early diagnosis of RA, thus supporting its potential as a novel disease biomarker.