From the Guidelines
The primary purpose of the Rapid Plasma Reagin (RPR) test is to screen for syphilis infection and monitor treatment response, with a positive result requiring confirmation with a treponemal-specific test due to the potential for false positives. The RPR test is a non-treponemal test that detects antibodies produced in response to Treponema pallidum infection, measuring the body's response to substances released during cellular damage caused by the infection 1. A positive RPR result indicates possible syphilis infection, but it is essential to confirm the diagnosis with a treponemal-specific test like TP-PA or FTA-ABS because RPR can produce false positives due to other conditions like autoimmune diseases, viral infections, or pregnancy 1.
Key Points
- The RPR test is used for initial screening, typically followed by a confirmatory test 1
- The test is useful for monitoring treatment response, with titers typically declining following successful therapy 1
- A fourfold decrease in titer within 6-12 months indicates adequate treatment for primary and secondary syphilis
- Regular follow-up RPR testing is essential to confirm treatment success
Treatment and Follow-up
The standard treatment for syphilis is penicillin G, with benzathine penicillin G 2.4 million units IM as a single dose for early syphilis or three weekly doses for late latent or tertiary syphilis 1. For penicillin-allergic patients, doxycycline 100mg twice daily for 14 days (early) or 28 days (late) can be used. It is crucial to follow up with RPR testing to document a decline in titers and confirm treatment success, using the same nontreponemal test used initially to document the infection 1.
From the Research
Purpose of the Rapid Plasma Reagin (RPR) Test
The Rapid Plasma Reagin (RPR) test is a screening test used for the diagnosis of syphilis 2. It is a nontreponemal test, which means it detects antibodies that are not specifically directed against the bacteria that cause syphilis, but rather against substances released by the bacteria.
Key Features of the RPR Test
- The RPR test is widely used as a screening test for syphilis, along with the Venereal Disease Research Laboratory (VDRL) test 2, 3.
- The test is used to monitor the response to treatment, with a decrease in RPR titers indicating a response to therapy 4, 5.
- The RPR test has a higher specificity than the VDRL test, but a lower sensitivity 3.
- Automated RPR tests, such as the HiSens Auto Rapid Plasma Reagin (AutoRPR) test, are available and can be used as an alternative to conventional RPR tests 3.
Clinical Applications of the RPR Test
- The RPR test is used to diagnose syphilis in its various stages, including primary, secondary, and latent syphilis 2, 4, 5.
- The test is also used to monitor the response to treatment in patients with syphilis, particularly in those with HIV infection 4, 5.
- In pregnant women, the RPR test is used as a screening test for syphilis, with positive results confirmed by treponemal tests such as the Fluorescent Treponemal Antibody (FTA-ABS) test 6.