ANTI-CYCLIC CITRULLINATED PEPTIDE ANTIBODIES AND RHEUMATOID FACTOR STABILITY IN EARLY INFLAMMATORY ARTHRITIS

Background: Autoantibodies associated with Rheumatoid Arthritis (RA) consist of Rheumatoid Factor (RF) and anti-citrullinated protein antibodies, including anti-Cyclic Citrullinated Peptide (anti-CCP). The presence of these antibodies is associated with worse outcomes. The stability of these antibodies in early disease and the factors affecting antibody levels require further study. Objectives: To determine whether anti-CCP and RF status remains stable in Early Inflammatory Arthritis (EIA). Methods: Data was collected from the Canadian Early Arthritis Cohort (CATCH), a prospective multicentre observational cohort of patients ≥16 years of age with symptom duration of 6 weeks up to 12 months and ≥2 swollen joints or ≥1 swollen small joint of the hand and ≥1 of positive rheumatoid factor, positive anti-CCP, morning stiffness ≥45 minutes, good response to non-steroidal anti-inflammatories or positive metatarsal-phalangeal squeeze test. Subjects were included in the analyses if anti-CCP and RF values were available at baseline and at least one follow-up visit. Results: Baseline and follow-up anti-CCP and RF values were available in 283 of the 1330 subjects enrolled in CATCH. Mean follow-up time was 23.7 months (range 12-72 months). At baseline, 169 (59.7%) were anti-CCP positive. Of these, 9 (5.4%) became anti-CCP negative during the follow-up period. Interestingly, 36 of the 114 anti-CCP negative patients (31.6%) became positive after a mean of 33 months. RF positivity at baseline was 177 (62.7%) and 27 (15.6%) of these patients became negative at follow-up. Nineteen of the 106 (17.1%) RF-negative patients seroconverted after a mean of 15.6 months. Table 1. Anti-CCP and RF status (N=283) AntibodyBaseline PositiveNegative to PositiveMean Time to SeroconversionPositive to NegativeMean Time to SeroconversionLast follow up Positive (%)(%)(months)(%)(months)(%) CCP169 (59.7)36 (31.6)339 (5.4)21.3196 RF177 (62.7)19 (17.1)15.627 (15.6)15.6169 Conclusions: Anti-CCP positivity appears relatively stable in EIA patients with positive anti-CCP at baseline. However, a large proportion of initially anti-CCP negative patients seroconverted later in disease. RF is more variable throughout disease course and shows a potential to convert and revert. These results are consistent with those from another large, recently published North American EIA cohort. Reasons for the high rate of seroconversion and variability are unknown, but may be secondary to the short disease duration at presentation, disease activity and treatment. Factors affecting antibody positivity and titers require further study. References: 1. van Venrooij WJ, Zendman AJ, Pruijn GJ, Autoantibodies to citrullinated antigens in (early) rheumatoid arthritis. Autoimmun Rev. 2006 Nov;6(1):37-41. 2. Guzian MC, Carrier N, Cossette P, de Brum-Fernandes AJ, Liang P, Ménard HA, Boire G. Outcomes in recent-onset inflammatory polyarthritis differ according to initial titers, persistence over time, and specificity of the autoantibodies. Arthritis Care Res. 2010 Nov;62(11):1624-32. Disclosure of Interest: L. Barra: None Declared, V. Bykerk Grant/Research support from: Pfizer, Amgen Inc, J. Pope: None Declared, P. Haraoui: None Declared, C. Hitchon: None Declared, C. Thorne: None Declared, E. Keystone Grant/Research support from: Pfizer, Amgen, Consultant for: Pfizer, Amgen, D. Ferland: None Declared, G. Boire: None DeclaredCitation: Annals of the Rheumatic Diseases, volume 70, supplement 3, year 2011, page 641Session: Rheumatoid arthritis – prognosis, predictors and outcome (Poster Presentations )