Reagin Ab

Syphilis tests generally look for certain antibodies in your blood. Antibodies are proteins that your immune system makes when it finds harmful substances in your body. In this case, the harmful substance is the bacterium that causes syphilis, one of the most common sexually transmitted infections (STIs.)

All syphilis tests are used to check your blood for signs of a syphilis infection. Like other STIs, syphilis spreads through vaginal, oral, or anal sexual contact with someone who has the infection. It can also pass during pregnancy to the fetus.