The immunodiffusion (ID) approach is the gold standard for anti–topoisomerase I antibody testing in systemic sclerosis (SSc), however enzyme-linked immunosorbent assay (ELISA) and multiple-bead technologies are frequently utilized in modern settings to reduce time and money. The purpose of this study was to evaluate the performance of the multiple-bead assay, ELISA, and ID testing procedures. Researchers performed a retrospective analysis at the University of Michigan on patients whose extractable nuclear antigen 10 autoantibody panel tested positive for anti–topo I antibody using multiple-bead technology over a one-year period. All positive multiple-bead assay samples were transported to RDL Laboratories and reflexed for ELISA, and all positive ELISA anti–topo I antibodies were further analyzed by ID. A rheumatologist analyzed the clinical data and looked for the existence of SSc. Frequency tables were used to evaluate the data. Physicians at the University of Michigan requested around 9500 extractable nuclear antigen 10 panels. 129 patients were shown to have anti–topo I antibodies by multiple-bead test, 51 by multiple-bead assay and ELISA, and 21 by multiple-bead assay, ELISA, and ID. The study discovered that 26.4 percent of patients who tested positive for SSc by multiple-bead assay, 47.1 percent by multiple-bead assay and ELISA, and 95.2 percent by multiple-bead assay, ELISA, and ID had SSc.
Multiple-bead tests provide a large number of false-positive findings for anti–topo I antibodies in patients who do not have clinical signs of SSc. The use of a stepwise method to validate positive multiple-bead assay findings using both ELISA and ID increases the predictive value of antibody testing for the diagnosis of SSc.
