From the Guidelines
If your RPR test shows a 1:1 titer and your treponema antibody test is negative, this most likely indicates a false positive RPR result rather than syphilis infection. The RPR is a non-treponemal test that can produce false positives due to various conditions including autoimmune diseases, viral infections, pregnancy, or laboratory error, as noted in the 2018 update by the Infectious Diseases Society of America and the American Society for Microology 1. The treponema antibody test (such as TP-PA or FTA-ABS) is more specific for syphilis, and its negative result strongly suggests you don't have syphilis.
Key Points to Consider
- The RPR test detects antibodies against cardiolipin, which can be produced in response to conditions other than syphilis, while the treponemal tests specifically detect antibodies against the syphilis-causing bacteria Treponema pallidum.
- No treatment is needed for a false positive RPR with negative treponemal antibodies.
- However, if you have risk factors for syphilis or symptoms concerning for the disease, your healthcare provider might recommend repeat testing in a few weeks to ensure the result wasn't due to very early infection, as suggested by the guidelines for treatment of sexually transmitted diseases 1.
Clinical Implications
- False positive RPR results can occur due to various medical conditions unrelated to syphilis, highlighting the importance of confirming results with a treponemal test.
- The use of only one type of test is insufficient for diagnosis, and both non-treponemal and treponemal tests should be used for accurate diagnosis, as recommended by the Infectious Diseases Society of America and the American Society for Microology 1.
From the Research
Interpretation of RPR 1:1 and Treponema Antibody Negative Results
- The RPR (Rapid Plasma Reagin) test is a non-treponemal test used to screen for syphilis, while treponemal tests, such as the FTA-ABS (Fluorescent Treponemal Antibody-Absorption) test, are used to confirm the diagnosis 2, 3.
- A negative treponemal test result, in combination with a positive RPR result (1:1), may indicate a false-positive RPR result or early infection with syphilis, where the treponemal antibodies have not yet developed 4, 5.
- The sensitivity and specificity of treponemal tests, such as the FTA-ABS test, are generally high, but may vary depending on the stage of the disease and the population being tested 3, 6.
- In some cases, treponemal tests may become non-reactive after treatment for syphilis, a phenomenon known as seroreversion 6.
- The results of the RPR and treponemal tests should be interpreted in the context of the patient's clinical history, physical examination, and other laboratory results 2, 5.