title: Anti-cyclic citrullinated peptide versus anti-Sa antibodies in diagnosis of rheumatoid arthritis in an outpatient clinic for connective tissue disease and spondyloarthritis.
abstract: OBJECTIVE
  . To compare the diagnostic value of anti-cyclic citrullinated peptide (anti-CCP) and anti-Sa antibodies in serum for prediction of rheumatoid arthritis (RA) in an outpatient clinic for connective tissue diseases and spondyloarthritides.
  
  
  METHODS
  A cross-sectional study was carried out to analyze the presence or absence of anti-CCP and anti-Sa antibodies in the sera of 250 randomly selected patients. The disease distribution in the study was as follows: 87 patients had RA (34.8%); 90 (36%) had other connective tissue diseases (CTD); 50 (20%) spondyloarthritis; 19 (7.6%) polymyalgia rheumatica; and 4 (1.6%) juvenile idiopathic arthritis.
  
  
  RESULTS
  Anti-CCP antibodies were detected in 63 patients with RA and in 9 patients with other illnesses [sensitivity 72.4%, specificity 94.4%, positive predictive value (PPV) 87.5%]. Anti-Sa antibodies were detected in 38 patients with RA and in 6 patients with other illnesses (sensitivity 43.6%, specificity 96.3%, PPV 86.3%). Anti-CCP and anti-Sa results were discordant in up to 47 of 87 RA patients. No relation between the presence of anti-Sa and higher or lower titers of anti-CCP antibodies was observed.
  
  
  CONCLUSIONS
  The diagnostic value in RA is similar for both antibodies. However, the sensitivity of anti-CCP detection is higher than that of anti-Sa. Our results suggest that presence of anti-Sa antibodies in serum may be useful as a complementary assay when anti-CCP antibodies are negative and RA is suspected.
authors.affiliation: Department of Rheumatology, Hospital General Universitario Gregorio Marañón, Madrid, Spain.
authors.forename: Francisco-Javier
authors.initials: FJ
authors.lastname: López-Longo
authors.forename: Margarita
authors.initials: M
authors.lastname: Rodríguez-Mahou
authors.forename: Silvia
authors.initials: S
authors.lastname: Sánchez-Ramón
authors.forename: Ana
authors.initials: A
authors.lastname: Estecha
authors.forename: Mónica
authors.initials: M
authors.lastname: Balsera
authors.forename: Rosa
authors.initials: R
authors.lastname: Plaza
authors.forename: Eduardo
authors.initials: E
authors.lastname: Fernández-Cruz
authors.forename: Luis Carreño
authors.initials: LC
authors.lastname: Pérez
mesh_terms: D000974:Antibodies, Antinuclear / Q000097:blood*; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000276:immunology; D001324:Autoantigens / Q000276:immunology*; D003240:Connective Tissue Diseases / Q000175:diagnosis / Q000276:immunology; D003937:Diagnosis, Differential; D006801:Humans; D010045:Outpatients; D010456:Peptides, Cyclic / Q000276:immunology*; D012680:Sensitivity and Specificity; D025241:Spondylarthritis / Q000175:diagnosis / Q000276:immunology
chemical_list: D000974:Antibodies, Antinuclear; D001324:Autoantigens; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide