Rheumatoid arthritis associated autoantibodies in patients with synovitis of recent onset

An inception cohort of 238 patients having peripheral joint synovitis of le ss than 12 months duration was evaluated clinically and followed prospectiv ely for 1 year to determine the clinical significance of a number of rheuma toid arthritis (RA) associated autoantibodies. Serum samples collected at t he time of the initial evaluation were tested for rheumatoid factor (RF) an d antibodies to Sa (anti-Sa), RA-33, (pro) filaggrin [antifilaggrin antibod y (AFA)], cyclic citrullinated peptide (anti-CCP), calpastatin, and keratin [antikeratin antibody (AKA)]. RF had a sensitivity of 66% and a specificit y of 87% for RA. Anti-Sa, AFA, and anti-CCP all had a specificity of more t han 90%, but a sensitivity of less than 50% for this diagnosis. Overall, th ere was a high degree of correlation between AFA, AKA, anti-Sa or anti-CCP, this being highest between anti-Sa and anti-CCP (odds ratio, 13.3; P < 0.0 01). Of the 101 patients who were positive for at least one of these four a utoantibodies, 57% were positive for only one. Finally, anti-Sa identified a subset of predominantly male RA patients with severe, erosive disease. An ti-Sa, AFA and anti-CCP are all specific for early RA but, overall, have li ttle additional diagnostic value over RF alone. Although these antibodies m ay preferentially recognize citrullinated antigens, the modest degree of co ncordance between them in individual patient sera suggests that it is unlik ely a single antigen is involved in generating these responses.