Treponema pallidum, the etiologic agent responsible for syphilis produces two kinds of antibodies in human infections. Treponemal antibodies can be detected by tests such as the Fluorescent Treponemal Antibody-Absorption (FTA-ABS) Test A or MHA-TP whereas the reagin antibody is detected by non-treponemal tests such as the RPR Antigen Card Test. In the presence of the reagin antibody in the reactive sample, the RPR Antigen preparation will produce flocculation consisting of black clumps against the white background of the test card. By contrast, non-reactive samples will yield an light-grey homogenous suspension.