Treponemal Syphilis Test in Colorado

What this test measures

Syphilis is a sexually transmitted infection that can develop in stages and may produce few or no obvious symptoms for long periods. Two broad categories of blood tests are used: nontreponemal tests, such as the RPR, which measure antibodies released during infection, and treponemal tests, which detect antibodies that bind Treponema pallidum directly. The two types answer slightly different questions.

The treponemal test requires a blood sample. It is commonly used as a confirmatory step after a reactive nontreponemal screen, and in some testing algorithms it is used first. Treponemal tests generally remain reactive for life, even after successful treatment, so they are better at showing that infection has occurred than at measuring current activity. Nontreponemal titers are used to follow activity over time.

The test may be ordered when screening suggests infection, when symptoms raise concern, or during a broader sexual health evaluation. A reactive treponemal result does not by itself indicate how recent or active an infection is, and a negative result may occur very early after exposure. Clinicians combine the result with a nontreponemal titer, symptoms, and history before reaching a conclusion.