In first 8 weeks of syphilis the most specific test is

The fluorescent treponemal antibody absorption (FTA-ABS) test is a blood test that checks for the presence of antibodies to Treponema pallidum bacteria(during first 8weeks of infection). These bacteria cause syphilis. Syphilis s a sexually transmitted infection (STI) that's spread through direct contact with syphilitic sores. Ref Harrison20th edition pg 1234