Isolated positive anti-SS-B autoantibodies are not related to clinical features of systemic autoimmune diseases: Results from a routine population survey

OBJECTIVE To assess in clinical practice the frequency and diagnosis associated with the SS-B-positive/SS-A negative autoantibody profile. METHODS We analyzed a one-year consecutive population of 624 patients referred by clinicians to the immunology laboratory to investigate anti-SS-A and/or anti-SS-B autoantibodies, who were detected using luminex technology. Data were analyzed for patients with isolated anti-SS-B autoantibodies. The clinical characteristics and diagnosis of connective tissue diseases (CTD) were retrieved according to the international criteria. RESULTS Among 1173 sera positive for anti-SS-A and/or anti-SS-B autoantibodies from 624 patients, we identified 84 patients (13.5%) that had isolated anti-SS-B. Among the 75 patients positive for anti-SS-B with known clinical data, 15 were diagnosed with a CTD (20%) including 4 systemic lupus erythematosus (5%), 4 rheumatoid arthritis (5%), 2 idiopathic inflammatory myositis (3%), 1 primary Sjögren's syndrome pSS (1%), 1 systemic sclerosis (1%), 2 undefined CTD (3%), and 1 mixed CTD (1%). Among the 60 other patients, 18 had non-CTD autoimmune diseases and 42 had non-autoimmune diseases. Within the CTD population, the presence of isolated anti-SS-B was not significantly associated to characteristic indicating a specific syndrome. There was no association between diagnosis of CTD and level of anti-SS-B autoantibodies (p = 0.70). Arthralgia was the more frequent sign and encountered in 10 patients (67%), of whom 3 had arthritis. CONCLUSION The presence of anti-SS-B, without anti-SS-A autoantibodies using luminex technology, was not associated with CTD, especially pSS, in daily clinical practice. Our data suggests that the SS-B serological profile is not contributive for the classification criteria of pSS.