Autoantibodies in biological agent naive patients with psoriatic arthritis.

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.