Laboratory diagnosis of syphilis with automated immunoassays

The serological detection of specific antibodies to Treponema pallidum is of particular importance in the diagnosis of syphilis. The purpose of this study was to evaluate diagnostic performances of automated immunoassays in comparison with T. pallidum hemagglutination test (TPHA) and Western Blot (WB). The retrospective study was performed with different panels of sera: 244 clinical and serological characterized syphilitic sera and 203 potentially interfering samples. All the sera were tested by Enzygnost Syphilis, ARCHITECT Syphilis TP, TPHA, and homemade WB. The diagnostic performances of the two assays were very similar: both Enzygnost Syphilis and ARCHITECT Syphilis TP performed with a sensitivity of 99.2%, whereas the specificity was 98.5 and 98.4%, respectively. Considering the suitability for automation, both immunoassays may represent a good choice as a screening test. However, the use of a confirmatory test, such as TPHA or WB, remains a must in order to avoid false-positive results.