Infection with Treponema pallidum provides two distinct categories of antibodies: (1) reagin (a nonspecific antibacterial antibody) and (2) antitreponemal antibody. Reagin tests, by their nature nonspecific, include the Wassermann and Reiter complement fixation tests, now seldom used. Reagin tests currently used for screening are the Venereal Disease Research Laboratory (VDRL) and rapid plasma reagin (RPR) flocculation tests. Because reagin screening tests often yield false-positive reactions (Table 3-12), positive test results are confirmed by means of treponemal antibody tests. The best of these is the fluorescent treponemal antibody-absorption test with absorbed serum.27