New coupled-particle light-scattering assay for detection of Ro/SSA (52 and 60 kilodaltons) and La/SSB autoantibodies in connective tissue diseases

The diagnostic and analytical performance of the coupled-particle light-sca ttering assay in detecting anti-Ro/SSA autoantibodies (the 60-kDa [Ro60] an d the 52-kDa [Ro52] antibodies) and anti-La/SSB autoantibodies was evaluate d. The antigens were obtained by recombinant DNA procedures to include the most immunogenic epitopes for each protein by using a prokaryotic expressio n system. Serum samples from 151 patients with connective tissue diseases a nd 52 control subjects (including patients with viral infections, patients with Lyme disease, and healthy subjects) were studied. Sensitivities for de tection of anti-Ro/SSA and anti-La/SSB were 88.2 and 95.2%, respectively; s pecificities were 97.6 and 98.1%, respectively. The intra-assay coefficient of variation (CV) ranged from 4.3 to 10.9% for anti-Ro/SSA and from 2.8 to 12.5% for anti-La/SSB; interassay CVs ranged from 6.5 to 13.2% and from 8. 2 to 14.5%, respectively. Among the anti-Ro/SSA-positive samples, Ro60 was recognized by 66% of the test sera and Ro52 was recognized by 95% of the te st sera. Thirty-four percent of the Ro/SSA-positive sera were reactive only with the Ro52 antigen, indicating that anti-Ro52 is the most common antibo dy specificity recognized by anti-Ro/SSA autoantibodies. No differences wer e found between the prevalences of anti-Ro60 and anti-Ro52 in relation to s ystemic lupus erythematosus or Sjogren's syndrome. The results of the prese nt study indicate that this new immunoassay is an efficient diagnostic tool for the detection of anti-Ro/SSA and anti-La/SSB antibodies in patients wi th autoimmune disorders.