Evaluation of three automated Treponema pallidum antibody assays for syphilis screening

The accuracy of the test is critical for the syphilis serology diagnosis. This study aims to evaluate the values of the Elecsys syphilis assay, the Architect syphilis assay, and the Mindray syphilis assay, as syphilis screening tests for pregnant women and patients with syphilis or other diseases. A reverse algorithm was used for the syphilis serology diagnosis. Serum samples (n = 584) were tested with three automated screening assays. All reactive sera by one, two, or three screening assays were further analyzed with the tolulized red unheated serum test (TRUST). Inconsistent results were confirmed by the Treponema pallidum particle agglutination assay (TPPA). The final patient diagnosis was made according to the results of syphilis serology, clinical evidence, and past medical history. The sensitivity, specificity, accuracy, and kappa value of each assay were as follows: for the Elecsys syphilis assay, 100.0%, 98.5%, 98.6%, and 0.927, respectively; for the Architect syphilis assay: 100.0%, 94.5%, 95.0%, and 0.770; and for the Mindray syphilis assay: 100.0%, 97.0%, 97.3%, and 0.862. The McNemar test showed that there were significant differences in the performance between the Elecsys syphilis assay and the Architect syphilis assay (P < 0.001), and between the Mindray syphilis assay and the Architect syphilis assay (P = 0.001). Our study demonstrated that three automated Treponema pallidum antibody assays generally showed high sensitivities and specificities, and so, they are suitable for use in screening for syphilis. The performances of the Elecsys syphilis assay and the Mindray syphilis assay are superior to Architect syphilis assay.