Development and comparative evaluation of immunoblot assays for detecting autoantibodies to Scl 70 and Jo 1 antigens in serum.

We developed rapid 24-h immunoblot assays for detecting autoantibodies to Scl 70 and Jo 1 antigens in serum. In comparative studies, we evaluated the analytical sensitivity of the immunoblot assays and commercial immunodiffusion assays for anti-Scl 70 and anti-Jo 1 autoantibodies with the use of positive control sera, and compared the frequencies of positive and negative results in a group of 116 sera, including specimens from 34 healthy controls and 82 patients with various connective-tissue diseases. The immunoblot assays were greater than 100-fold more sensitive than immunodiffusion for detecting both autoantibodies. Despite greater analytical sensitivity, there were no false-positive results by the immunoblot assay for anti-Scl 70 or anti-Jo 1 autoantibodies in sera from either the controls or the patients. The diagnostic sensitivity of the immunoblot assay for anti-Scl 70 autoantibodies in patients with scleroderma was greater than that of the immunodiffusion assay, 70% vs 20%, and was equivalent in patients with polymyositis, 43%. We conclude that rapid immunoblot assays for anti-Scl 70 and anti-Jo 1 autoantibodies are superior to immunodiffusion assays for clinical use and are suitable for routine use in the clinical laboratory.