treponemalspecific

Treponemal-specific refers to antibodies or diagnostic tests that are directed against Treponema pallidum, the bacterium responsible for syphilis, or to antigens shared by treponeme species. In clinical laboratory testing, treponemal-specific tests detect antibodies that react with Treponema pallidum treponemal antigens. These tests are used to diagnose syphilis and, in some cases, other treponemal diseases such as yaws, bejel, or pinta.

Treponemal-specific tests are distinct from non-treponemal tests, which detect reagin-type antibodies that are not unique to Treponema pallidum and can occur in various conditions. Common treponemal tests include the fluorescent treponemal antibody absorption test (FTA-ABS), the treponemal pallidum particle agglutination assay (TPPA), and various treponemal enzyme immunoassays or chemiluminescent immunoassays. These tests are generally more specific than non-treponemal tests, but their results require careful interpretation in the clinical context.

A key feature of treponemal tests is that once positive, they often remain reactive for life, even after successful treatment. Therefore, they are not used alone to assess current disease activity or therapeutic response; non-treponemal titers are typically monitored for such purposes. In screening algorithms, some programs use treponemal tests as the initial screen (reverse sequence screening), followed by non-treponemal testing to evaluate activity and need for treatment, with a second treponemal test for confirmation in ambiguous cases.

Limitations include occasional false positives in other treponemal diseases or certain autoimmune conditions, and occasional false negatives in very early primary disease or in immunocompromised individuals.