Syphilis could be diagnosed by having a doctor take a swab sample from an active sore. If an individual just wants to get tested for syphilis a Rapid Plasma Reagin (RPR). This test would just screen for the syphilis antibodies. Syphilis is usually detected within two to six weeks after coming in contact with the bacteria. To be 100% safe I would suggest getting tested for all STDs three months after the last time an individual had sex.
Syphilis typically isn't undetected by a blood test. However, an individual with syphilis may not show symptoms of the bacteria. If syphilis is treated in the early stages, it can be cured with antibiotics. A person who has syphilis will often test positive for the bacteria for life. Seem the body already built up the antibodies. A doctor will usually ask a patient to return for a check up to ensure that the bacteria isn't contagious.