title: Autoantibodies in biological agent naive patients with psoriatic arthritis.
abstract: BACKGROUND
  Anti-tumour necrosis factor alpha (anti-TNFalpha) treatment may be associated with the production of autoantibodies, including lupus-specific autoantibodies.
  
  
  OBJECTIVE
  To investigate the prevalence of autoantibodies in biological agent naive patients with psoriatic arthritis (PsA).
  
  
  METHODS
  94 consecutive, prospectively collected, biological agent naive patients with PsA at the University of Toronto PsA clinic underwent clinical and laboratory assessment. Disease activity was assessed by the number of actively inflamed joints, and the Psoriasis Activity and Severity Index (PASI) score. Antinuclear antibodies (ANA), rheumatoid factor (RF), double stranded DNA (dsDNA), Ro, La, Smith, and RNP were tested. Descriptive statistics and non-parametric tests were used to analyse the data.
  
  
  RESULTS
  44/94 (47%) patients with PsA were ANA positive (>/=1/40); 13/94 (14%) had a clinically significant titre of >/=1/80. Three per cent had dsDNA antibodies, 2% had RF and anti-Ro antibodies, 1% had anti-RNP antibodies, and none had anti-La or anti-Smith antibodies.
  
  
  CONCLUSIONS
  The background prevalence of ANA >/=1/80 in patients with PsA was 14%, with very few patients having specific lupus antibodies. This should serve as a baseline figure for the frequency of autoantibodies in biological agent naive patients with PsA for studies of the use of anti-TNFalpha agents.
authors.affiliation: Centre for Prognosis Studies in the Rheumatic Diseases, Division of Rheumatology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: S R
authors.initials: SR
authors.lastname: Johnson
authors.forename: C T
authors.initials: CT
authors.lastname: Schentag
authors.forename: D D
authors.initials: DD
authors.lastname: Gladman
mesh_terms: D000328:Adult; D000368:Aged; D000974:Antibodies, Antinuclear / Q000097:blood; D018501:Antirheumatic Agents / Q000276:immunology; D015535:Arthritis, Psoriatic / Q000188:drug therapy / Q000276:immunology* / Q000473:pathology; D001323:Autoantibodies / Q000097:blood*; D001324:Autoantigens; D005260:Female; D006801:Humans; D007155:Immunologic Factors / Q000276:immunology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012016:Reference Values; D012261:Ribonucleoproteins / Q000276:immunology; D012720:Severity of Illness Index; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors; D000097585:SS-B Antigen
chemical_list: D000974:Antibodies, Antinuclear; D018501:Antirheumatic Agents; D001323:Autoantibodies; D001324:Autoantigens; D007155:Immunologic Factors; D012261:Ribonucleoproteins; D014409:Tumor Necrosis Factor-alpha; D000097585:SS-B Antigen