Should Anti-citrullinated Protein Antibody and Rheumatoid Factor Status Be Reassessed During the First Year of Followup in Recent-Onset Arthritis? A Longitudinal Study

• Published in: Journal of rheumatology Vol. 38; no. 11; pp. 2336 - 2341
• Main Authors: MJAAVATTEN, Maria D, VAN DER HEIJDE, Desiree M, UHLIG, Till, HAUGEN, Anne J, NYGAARD, Halvor, BJØRNEBOE, Olav, KVIEN, Tore K
• Format: Journal Article
• Language: English
• Published: Toronto, ON Journal of Rheumatology Publishing 01-11-2011
• Subjects: Adolescent; Adult; Aged; Antibodies, Anti-Idiotypic - blood; Arthritis, Rheumatoid - blood; Arthritis, Rheumatoid - classification; Arthritis, Rheumatoid - diagnosis; Biological and medical sciences; Cohort Studies; Disability Evaluation; Disease Progression; Diseases of the osteoarticular system; Female; Follow-Up Studies; Humans; Immunoglobulin M - blood; Inflammatory joint diseases; Longitudinal Studies; Male; Medical sciences; Middle Aged; Miscellaneous. Osteoarticular involvement in other diseases; Peptides, Cyclic - immunology; Phenotype; Rheumatoid Factor - blood; Severity of Illness Index; Young Adult; Autoimmunity; AUTOANTIBODIES; Immunopathology; Antibody; ANTICYCLIC CITRULLINATED ANTIBODIES; Diseases of the osteoarticular system; Rheumatology; Autoantibody; Autoimmune disease; Inflammatory joint disease; Arthritis; LONGITUDINAL STUDY; Protein; Rheumatoid factor; Chronic; Rheumatoid arthritis
• ISSN: 0315-162X; 1499-2752
• DOI: 10.3899/jrheum.110234

Presence and levels of antibodies contribute to the classification of rheumatoid arthritis. We investigated the longitudinal course of anti-citrullinated protein antibodies (ACPA) and immunoglobin M (IgM) rheumatoid factor (RF) during the first year after arthritis onset in patients with very short disease duration.
Patients (aged 18-75 years) with ≥ 1 swollen joint of ≤ 16 weeks' duration had assessments of ACPA (2nd generation anti-cyclic citrullinated peptide antibodies, anti-CCP2) and IgM RF at inclusion and after 3, 6, and 12 months. Frequencies of seroconversions (negative to positive and vice versa) and changes in antibody levels during followup were determined.
A total of 281 early arthritis patients (median duration of joint swelling 32 days, 14.2% ACPA positives, 12.8% IgM RF positives) with 978 longitudinally collected serum samples were included. Only 5 patients (1.8%) negative for both antibodies at baseline turned antibody-positive during followup, while 9 antibody-positive patients (3.2%) turned antibody-negative. ACPA was more stable than RF regarding both status and levels.
Antibody status (ACPA/RF) is a stable phenotype in very early arthritis, as seroconversion was only found in 5% of patients. Repeated measurement of ACPA or RF during the first year after onset of arthritis does not offer major additional information.