Syphilis is caused by Treponema pallidum . Laboratory diagnosis is with both treponemal and non-treponemal antibody detection. Different algorithms for testing are in use with individual advantages and disadvantages. There are three recognised algorithms. The “traditional” algorithm uses the non-treponemal assay such as the rapid plasma regain (RPR) for primary evaluation followed by a confirmatory treponemal assay for reactive samples only. It is cost-effective and suited to resource-limited settings. The second is the reverse algorithm which uses a treponemal assay first followed by a non-treponemal assay for reactive samples. When a new diagnosis of syphilis is made or if a discordant result is obtained, a second confirmatory treponemal assay such as the T. pallidum particle agglutination (TPPA) assay is generally used. The third is the European Centre for Disease Prevention and Control algorithm, in which syphilis screening begins with a treponemal immunoassay that is followed by a second, different treponemal assay as a confirmatory test in high prevalence populations. The traditional algorithm is markedly less sensitive in diagnosing syphilis. Non-treponemal tests are unnecessary in diagnosis but can be used for determining serological activity. Multiple factors, including prevalence, volume of testing and cost, should be considered before implementation of a specific algorithm.
Robert Norton (Sun,) studied this question.