Prevalence of systemic autoimmune rheumatic diseases and clinical significance of ANA profile: data from a tertiary hospital in Shanghai, China

It is necessary and useful to explore prevalence of various systemic autoimmune rheumatic diseases (SARDs) in patients with suspicion of having SARDs and to characterize antinuclear antibodies (ANA) profile for identifying different populations (SARDs and non-SARDs). A total of 5024 consecutive patients with available medical records were investigated, whose sera had been tested for ANA profile, including ANA, anti-dsDNA and anti-extractable nuclear antigen (ENA) antibodies, between 31 January 2012 and 26 March 2014. Only 594 (11.8%) patients were diagnosed with SARDs of those suspected with SARDs. The prevalence of systemic lupus erythematosus (SLE) was highest (3.2%), followed by rheumatoid arthritis (RA) (2.5%), primary Sjogren's syndrome (pSS) (1.7%), ankylosing spondylitis (AS) (1.5%), etc. Of females, SLE also showed the highest prevalence (6%), while of males, AS showed the highest prevalence (1.9%). The prevalence of most SARDs was closely associated with age, except mixed connective tissue disease (MCTD), and the variation characteristics among different age groups were different among various SARDs. The prevalence of ANA was significantly increased in most SARD patients [especially in SLE, systemic sclerosis (SSc) and MCTD]. For anti-ENA antibodies, in contrast to some autoantibodies associated with multiple SARDs (e.g. anti-SSA, SSB, nRNP), others were relatively specific for certain diseases, such as anti-dsDNA, Sm, histone, nucleosome and Rib-P for SLE, anti-SCL-70 for SSc and anti-Jo-1 for polymyositis/dermatomyositis (PM/DM). Of note, ANA profile appeared to be of little significance for AS, ANCA-associated vasculitis (AAV), polymyalgia rheumatic (PMR), adult-onset Still's disease (ASD) and Behcet's disease (BD). The younger were more likely to have the presence of anti-dsDNA, Sm, histone or Rib-P for SLE, and anti-SSA for RA or MCTD. No significant differences for frequencies of ANA and anti-ENA autoantibodies were found between sexes in most SARDs, with the exception of RA and AS. The present study suggests that, of patients with SARDs-like clinical manifestations, the proportion of those with true SARDS is small, for most of whom tests for autoantibodies are necessary and useful to help make a prompt and precise diagnosis.