Independent associations of anti-cyclic citrullinated peptide antibodies and rheumatoid factor with radiographic severity of rheumatoid arthritis

ABSTRACT

Recent studies have established a strong association between anti-cyclic citrullinated peptide antibody [anti-CCP] positive rheumatoid arthritis [RA] and carriage of shared epitope [SE] alleles. Although anti-CCP have also been associated with more severe RA, the issue of whether this is independent of rheumatoid factor [RF] has not been addressed. To indentify associations between RF, anti-CCP, SE status and radiological damage, we studied a large cross-sectional cohort with longstanding RA. Individuals [n=100] enrolled in the study all fulfilled the American College of Rheumatology criteria for RA had a minimum disease duration of 4 years, and at least one definite radiographic erosion was present in hands or feet. Radiographs were scored blind at study entry by a single musculoskeletal radiologist using a modified Larsen's score, Anti-CCP and RF levels were determined using enzyme-linked immunosorbent assay, and DRBI typing was performed using polymerase chain reaction based methodology. Both anti-CCP and RF status, evidence of independent associated with radiographic severity [P<0.0001]. In subgroups stratified for both anti-CCP and RF status, evidence of independent associations of both antibodies with radiographic outcome was found [P<0.0001]. An association of SE alleles playing at most a secondary role. Our study support the view that previously described associations between SE and radiological severity, especially in RF-negative patients, may be indirect and due to an association with anti-CCP