Main Results
The traditional syphilis testing algorithm has been to screen with a nontreponemal test such as the VDRL, RPR, or TRUST and confirm reactive test results or clinical impressions with a treponemal test. Although the specificity of the nontreponemal tests is not as good as that of the treponemal tests, the per test cost of these tests are low compared to treponemal tests such as the fluorescent treponemal antibody-absorption (FTA-ABS) test, the Treponema pallidum particle agglutination (TPPA) test, and the enzyme immunoassay (EIA). Due to the development of easier to perform and automated treponemal tests such as EIA, the algorithm for screening with a treponemal test has become more widely used. Treponemal tests are more specific, more likely to be positive in late latent or late syphilis, less sensitive to room temperature extremes, and less likely to exhibit prozone reactions caused by excessive amounts of antibody. The ability to automate the EIA test is its biggest advantage and the reason that many laboratories are switching to screening with a treponemal EIA. However, a nontreponemal test is still needed to distinguish old from new infections, to determine treatment efficacy or failure, and to detect reinfections. Nontreponemal tests can be titered to follow treatment efficacy. Therefore, all reactive EIA test results should be confirmed with a nontreponemal test. If the nontreponemal test is also reactive, the patient has syphilis. If the EIA test result is reactive and the nontreponemal test is nonreactive, the EIA test should be repeated. If still reactive, a second treponemal test should be done. If the second treponemal test result is reactive, determination has to be made as to whether the person has had treated syphilis or possible late latent or late syphilis.