Syphilis: Treponemal Antibodies, Treponema pallidum Particle Agglutination (TPPA)

The Treponema pallidum particle agglutination (TPPA) test is employed to demonstrate treponemal antibodies during syphilis evaluation and is commonly paired with a nontreponemal assay (such as RPR) within current screening workflows. It functions as a treponemal-specific confirmation test and is not intended as a stand-alone general screening assay or for assessing treatment response. Universal prenatal screening programs may include TPPA for syphilis testing during pregnancy.

Treponema pallidum causes syphilis and is transmitted most often through sexual contact or by vertical transmission. Following infection, the humoral response produces IgM and subsequently IgG antibodies to treponemal antigens, and treponemal antibody tests demonstrate sensitivity across disease stages, including early infection. TPPA is a treponemal-specific agglutination assay that generally remains reactive long term after infection and after therapy; it should not be used to gauge treatment response. Nontreponemal titers (for example, RPR) are used to monitor disease activity and therapeutic effect. Biological false-positive reactivity can occur, and reactive results may be seen in nonvenereal treponematoses such as yaws and pinta. Interpretation requires correlation with clinical findings and other laboratory data.