Detection of anti-SSA antibodies by indirect immunofluorescence

Background: HEp-2 cells that overexpress the human 60-kDa SSA antigen have been used to improve sensitivity and specificity for the detection of anti-SSA antibodies by indirect immunofiuorescence. We describe a survey on the detection of anti-SSA antibodies using a commercial substrate that overexpresses SSA. Methods: The evaluation was done on 18 371 consecutive samples submitted to the laboratory for detection of anti-nuclear antibodies, from which 188 anti-SSA antibody-containing and clinically documented samples were obtained. The presence of anti-SSA antibodies produced a distinct bright speckled pattern with nucleolar staining in 10-20% of interphase cells. The identity of all anti-SSA antibodies was confirmed by dot-blot analysis. Results: Samples containing anti-SSA antibodies were separated into three main groups: group I, distinctive SSA pattern' and other nuclear staining (50%); group II, only the distinctive SSA pattern (29%); group III, nuclear staining but without the distinctive SSA pattern (21%). Anti-SSA antibodies with concurrent SSB antibodies were associated with group 1, whereas anti-SSA antibodies with concurrent U,-RNP antibodies were associated with group III. Group I included mainly patients with * Sjogren syndrome and systemic lupus erythernatosus (SLE), whereas group III included patients with mixed connective tissue disease and SLE. Diseases not classically associated with the presence of anti-SSA antibodies were found in group II in >50% of the cases. Conclusions: SSA-positive individuals were identified in a population selected on the basis of HEp-2000 positivity. Our study highlights diseases associated with anti-SSA antibodies and associations between the presence of the distinctive SSA pattern on HEp-2000 and some clinical conditions. (C) 2004 American Association for Clinical Chemistry.