Final answer:
The two non-treponemal antibody tests used to screen for syphilis are Rapid Plasma Reagin (RPR) and Venereal Disease Research Laboratory (VDRL), followed by confirmatory treponemal tests.
Step-by-step explanation:
The two non-treponemal antibody tests used as screening tests for syphilis are Rapid Plasma Reagin (RPR) and Venereal Disease Research Laboratory (VDRL). These tests detect nonspecific antibodies for lipid antigens that are produced during infection. They are useful because they give an indication of active infection and can be used to monitor the response to therapy. However, confirmatory testing must be done using treponemal tests, such as TP-PA or FTA-ABS, which test for antibodies to actual spirochete antigens.
Treponemal tests are used for confirmation since they specifically measure antibodies directed against Treponema pallidum antigens. Meanwhile, non-treponemal tests can sometimes result in false positives or false negatives due to their sensitivity and the nonspecific nature of the antibodies they detect. This is why it's important to use both types of tests for a reliable diagnosis of syphilis.