AUTOANTIBODY TESTING FOR CONNECTIVE-TISSUE DISEASES - COMPARISON OF IMMUNODIFFUSION, IMMUNOBLOT, AND ENZYME-IMMUNOASSAY

We evaluated 500 consecutive patient serum samples for the presence of six autoantibodies by three antibody detection methods: immunodiffusi on, immunoblot, and enzyme immunoassay. Clinical data were reviewed fo r each patient with positive antibody test results. Serum samples from 60 patients revealed antibodies to Sm, ribonucleoprotein (RNP), SSA/R o, SSB/La, Scl-70, or Jo-1. There were 7 false-positive test results ( 1%). All three methods detected autoantibodies in 36 (68%) of 53 patie nts with connective tissue disease. Immunoblot was the most sensitive method to detect autoantibodies (92%). Enzyme immunoassay and immunodi ffusion were less sensitive (81% and 74%, respectively). Antiribonucle oprotein and anti-SSB/La antibodies were more often detected by immuno blotting, whereas anti-SSA/Ro antibodies were more often detected by e nzyme immunoassay. Newer antibody detection methods (immunoblot and en zyme immunoassay) are less time consuming than immunodiffusion and sho w good interassay sensitivity without loss of specificity. A combinati on of immunoblot and enzyme immunoassay yielded excellent assay sensit ivity (100%) and specificity (99%) for detection of autoantibodies.