Interpret syphilis serology results in consultation with an experienced colleague. Health care professionals should consider yaws, pinta, bejel and Lyme disease in the differential diagnosis when NTT and/or TT are positive. Note: The following information is provided for general guidance. Refer to the follow-up section for recommendations related to monitoring of NTT results post treatment. If these diagnoses are suspected, it is appropriate to add a TT to the initial screen or, in the case of primary syphilis, to repeat both the TT and NTT after two (2) to four (4) weeks, when testing may have been done before seroconversion(incubation period). The NTT may be non-reactive in cases of early primary, late latent syphilis or tertiary syphilis. NTT antibody titres usually correlate with disease activity and can help stage infection, monitor response to treatment and detect re-infection. False positive serologic tests for syphilis may occur with certain conditions such as collagen-vascular disease, pregnancy, injection drug use, Lyme Disease or a condition inherent to the test or testing technique. Once reactive, TTs usually remain reactive for life regardless of treatment, although 15% to 25% of people will serorevert if treated during the primary stage Footnote 7. Although EIA is highly sensitive, it may lack specificity therefore if the EIA screen is positive, a second treponemal-specific test can confirm the diagnosis. Several commercial EIAs have been developed to detect IgG or IgM to specific T. ![]() TTs such as the treponemal-specific enzyme immunoassay (EIA) are more sensitive tests for syphilis. A second confirmatory TT may be done in some laboratories. An alternative approach is to use a reverse sequence algorithm, which uses a TT to screen and a quantitative NTT to confirm the positives. The traditional algorithm uses a non-treponemal test (NTT) -typically a rapid plasma reagin (RPR) test- to screen sera, followed by one (1) or two (2) TTs on the positive samples. Consult your local laboratory regarding testing protocols. Most provinces and territories use the reverse algorithm. Two (2) types of serologic screening algorithms are used in Canada Footnote 6. Serologic testing should always be done regardless of suspected stage. Refer to the Canadian Paediatric Society's article Congenital syphilis: No longer just of historical interest for information about how to manage infants born to mothers with reactive treponemal tests (TTs) during pregnancy. Test infants presenting with signs or symptoms compatible with early congenital syphilis even if their mother was seronegative at delivery because they may have become infected near term.
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