Objectives To determine the diagnostic value of autoantibodies (Ab) directed against citrullinated recombinant rat filaggrin (ACRFA) for very early RA.
Methods From a population-based recruitment, 152 patients with early (median disease duration:4 months [2‑6 mo]) peripheral arthritis (swelling of at least 2 joints persisting > 4 weeks) were studied. Follow-up period was 1 year. At the end of the study, patients were classified as RA (n = 88) or as other rheumatic diseases. Four Ab: rheumatoid factors (RF-IgM), anti-keratin Ab (AKA), anti-perinuclear factor (APF) and ACRFA by an ELISA whose result are expressed as the difference of OD values given by sera tested against the citrullinated and non-citrullinated forms of filaggrin were tested at entry.
Results Characteristics of these markers for RA are reported in the Table 1. Specificity of ACRFA was better than that of RF, APF and to a lesser degree AKA. Sensitivity of ACRFA was higher than that of AKA which is the single test still routinely used for detection of AFA. AKA, APF and ACRFA were complementary since certain sera were positive for only one test. Only 5/48 (10.5%) RF-negative RA patients were positive for ACRFA.
Conclusion AFA detected by a new ELISA have a higher diagnostic value for RA than AFA identified by previous tests in this population-based cohort of very early arthritis.
Study granted by the Fondation de la Recherche Médicale (FRM), the Association de Recherche sur la Polyarthrite (ARP) and for clinical assessment Pharmacia-Searle, France.