T pallidum Screening Cascade
Treponema pallidum (Syphilis) Screening Cascade
Serological test for screening for syphilis infection. This panel includes a Treponema-specific test which may be positive in all stages of syphilis. It may be positive with treponemal infections other than syphilis (bejel, pinta, yaws). Like FTA-ABS and TP-PA, once positive, it remains so; it cannot be used to judge the effectiveness of treatment.
The traditional syphilis screening approach when the first-line test is a nontreponemal assay (like RPR) and if positive, the second-line confirmatory test is a treponemal test (such as TP-PA) was developed many years ago when treponemal tests lacked necessary sensitivity but delivered acceptable specificity. In the early 1990s, the CDC published guidelines that recommended the traditional algorithm for screening. Since that time, a number of new, more sensitive treponemal immunoassays have been introduced. In 2008, the CDC issued a report that describes the new syphilis screening approach in which the treponemal test was used as the first-line test, and if positive, reflexes to the nontreponemal test. This report shows that a number of infected individuals would be missed using the traditional approach. In addition, a number of tested individuals would receive false-positive results
The implementation of the new approach−if the highly sensitive and specific treponemal assay is used−allows for an improvement in the early detection of syphilis infection that should lead to more effective treatment while preventing the spread of disease. When the treponemal test is positive, it will reflex to qualitative RPR and, if positive, reflex to RPR titer. If the RPR is negative, it will reflex to another (second) treponemal test for confirmation.
0.5 mL (Note: This volume does not allow for repeat testing.)
Red-top tube or gel-barrier tube
Stable at room temperature for seven days, refrigerated for 14 days, or frozen for 14 months.
Hemolysis; lipemia; gross bacterial contamination; plasma specimen