A novel bead-based assay to detect specific antibody responses against <it>Toxoplasma gondii </it>and <it>Trichinella spiralis </it>simultaneously in sera of experimentally infected swine

<p>Abstract</p> <p>Background</p> <p>A novel, bead-based flow cytometric assay was developed for simultaneous determination of antibody responses against <it>Toxoplasma gondii </it>and <it>Trichinella spiralis </it>in pig serum. This high throughput screening assay could be an alternative for well known indirect tests like ELISA. One of the advantages of a bead-based assay over ELISA is the possibility to determine multiple specific antibody responses per single sample run facilitated by a series of antigens coupled to identifiable bead-levels. Furthermore, inclusion of a non-coupled bead-level in the same run facilitates the determination of, and correction for non-specific binding. The performance of this bead-based assay was compared to one <it>T. spiralis </it>and three <it>T. gondii </it>ELISAs. For this purpose, sera from <it>T. gondii </it>and <it>T. spiralis </it>experimentally infected pigs were used. With the experimental infection status as gold standard, the area under the curve, Youden Index, sensitivity and specificity were determined through receiver operator curve analysis. Marginal homogeneity and inter-rater agreement between bead-based assay and ELISAs were evaluated using McNemar's Test and Cohen's kappa, respectively.</p> <p>Results</p> <p>Results indicated that the areas under the curve of the bead-based assay were 0.911 and 0.885 for <it>T. gondii </it>and <it>T. spiralis</it>, respectively, while that of the <it>T. gondii </it>ELISAs ranged between 0.837 and 0.930 and the <it>T. spiralis </it>ELISA was 0.879. Bead-based <it>T. gondii </it>assay had a sensitivity of 86% and specificity of 96%, while the ELISAs ranged between 64-84% and 93-99%, respectively. The bead-based <it>T. spiralis </it>assay had a sensitivity of 68% and specificity of 100% while the ELISA scored 72% and 95%, respectively. Marginal homogeneity was found between the <it>T. gondii </it>bead-based test and one of the <it>T. gondii </it>ELISAs. Moreover, in this test combination and between <it>T. spiralis </it>bead-based assay and respective ELISA, an excellent inter-rater agreement was found. When results of samples before expected seroconversion were removed from evaluation, notably higher test specifications were found.</p> <p>Conclusions</p> <p>This new bead-based test, which detects <it>T. gondii </it>and <it>T. spiralis </it>antibodies simultaneously within each sample, can replace two indirect tests for the determination of respective antibodies separately, while performing equally well or better.</p>