A critical evaluation of enzyme immunoassays for detection of antinuclear autoantibodies of defined specificities: I. Precision, sensitivity, and specificity

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Abstract
Objective To determine the performance characteristics of enzyme-based immunoassay (EIA) kits for the detection of antinuclear and other autoantibodies of defined specificities. Methods Nine manufacturers of EIA kits to detect antibodies of defined specificities participated in a study in which they received coded sera from the Centers for Disease Control and Prevention. These coded sera contained different dilutions of antibody of one specificity mixed with sera containing antibodies of other specificities. The manufacturers were asked to use their standard technology to determine antibody content and send the data to a committee of the International Union of Immunological Societies for analysis. The data were analyzed for sensitivity and specificity in the detection of anti–double-stranded DNA (anti-dsDNA), anti–single-stranded DNA, antihistone, anti-Sm, anti–U1 RNP, anti-SSA/Ro, anti-SSB/La, anti–Scl-70 (DNA topoisomerase I), anticentromere, and anti–Jo-1 antibodies. In addition, replicate samples were included in the coded sera to evaluate the precision of each EIA method. Results Lack of sensitivity and specificity was most evident in the anti-dsDNA and anti-Sm kits, although 2 kits for anti-dsDNA achieved acceptable sensitivity and specificity. Generally, anti-SSA/Ro, anti-SSB/La, anti–Scl-70, anticentromere, and anti–Jo-1 kits performed well. Many false-positive results were obtained with a multiple myeloma serum containing cryoprecipitates, but multiple myeloma sera without cryoprecipitates presented no problem in the EIA system. Precision, based on evaluation of replicate samples, varied from very good to poor. Conclusion No single manufacturer was clearly superior to others in terms of their products' overall sensitivity, specificity, and precision. Areas that needed improvement were in kits for the detection of antibodies to dsDNA and to Sm antigen. Some EIA kits achieved good sensitivity and specificity. Individual manufacturers were informed of the performance of their respective kits so they could take measures to correct perceived deficiencies and thus improve the reliability of a group of important diagnostic assays used in the evaluation of systemic rheumatic diseases.