Syphilis is a chronic infectious disease caused by sexual or congenital transmission of the Treponema pallidum spirochete. The disease progresses through distinct stages of infection characterized by diverse clinical symptoms. The appearance of a sore or chancre at the site of infection (primary stage) is followed by a generalized skin rash (secondary stage). If untreated, after a variable interval of latency the infection may progress to cardiovascular problems or neurosyphilis (tertiary stage).
Serological testing is essential in the detection and control of syphilis infection. According to the CDC STD Treatment Guidelines, presumptive diagnosis of syphilis is possible with the use of two types of serologic tests used in conjunction: Non-treponemal and Treponemal tests. Treponemal tests, such as the LIAISON® assay, EIAs, FTA-ABS and TP-PA, detect antibodies to Treponema pallidum and therefore indicate the specific cause of infection. Non-treponemal tests, such as RPR and VDRL, detect non-specific antibodies to cardiolipin which are present during acute conditions and can distinguish between active and past infection if the Treponemal test is positive. Non-treponemal tests alone are insufficient for diagnosis because false positive non-treponemal test results are sometimes associated with various medical conditions unrelated to syphilis.1,2
Historically, syphilis screen has been performed with a non-treponemal test with reflexive testing of positive results by a treponemal test. Recently, many clinical laboratories have adopted treponemal tests for screening purposes because of the improved performance as well as the ability to automate high testing volumes. With this testing protocol, not only is labor reduced, but higher specificity means fewer initially positive results in need of confirmation.
DiaSorin offers a Treponema assay on the LIAISON® systems.
1. Pope, Victoria, Infect. Med. 21 (8):339-404,2004. Cliggott Publishing, division of CMP Healthcare Media