This is a test for the antibody titre in the blood of a patient using live or killed syphilis-causing bacteria, Treponema pallidum. It becomes positive 4 to 6 weeks after infection and becomes negative in 2 years if treatment is successful. FTA-ABS is referred to as the "treponemal antigen test" because treponema pallidum is used as an antigen to make the measurement. This test is more sensitive and specific than the VDRL test.