The RPR test is an effective screening test, as it is very good at detecting people without symptoms who are affected by syphilis. However the test may suggest that people have syphilis who in reality do not (i.e., it may produce false positives). False positives can be seen in viral infections (Epstein-Barr, hepatitis, varicella, measles), lymphoma, tuberculosis, malaria, endocarditis, connective tissue disease, pregnancy, autoimmune diseases, intravenous drug abuse, or contamination. It can also occur naturally in the elderly.[1] As a result, these two screening tests should always be followed up by a more specific treponemal test. Tests based on monoclonal antibodies and immunofluorescence, including Treponema pallidum hemagglutination assay (TPHA) and Fluorescent Treponemal Antibody Absorption (FTA-ABS) are more specific and more expensive. Unfortunately, false positives can still occur in related treponomal infections such as yaws and pinta. Tests based on enzyme-linked immunoassays are also used to confirm the results of simpler screening tests for syphilis.
From Wikipedia:
The RPR test is an effective screening test, as it is very good at detecting people without symptoms who are affected by syphilis. However the test may suggest that people have syphilis who in reality do not (i.e., it may produce false positives). False positives can be seen in viral infections (Epstein-Barr, hepatitis, varicella, measles), lymphoma, tuberculosis, malaria, endocarditis, connective tissue disease, pregnancy, autoimmune diseases, intravenous drug abuse, or contamination. It can also occur naturally in the elderly.[1] As a result, these two screening tests should always be followed up by a more specific treponemal test. Tests based on monoclonal antibodies and immunofluorescence, including Treponema pallidum hemagglutination assay (TPHA) and Fluorescent Treponemal Antibody Absorption (FTA-ABS) are more specific and more expensive. Unfortunately, false positives can still occur in related treponomal infections such as yaws and pinta. Tests based on enzyme-linked immunoassays are also used to confirm the results of simpler screening tests for syphilis.