RPR | Syphilis Testing

RPR (Rapid Plasma Reagin) test – is a non-specific serological blood test used for detecting and monitoring syphilis infection. The test helps evaluate whether the human body reacts to Treponema pallidum – the bacterium that causes syphilis. The RPR test is often performed alongside specific syphilis tests such as TPHA or FTA-ABS.

A positive RPR reaction usually occurs 4–6 weeks after infection, when the body begins producing reagin – antibodies against lipid components that appear due to tissue damage caused by treponemal infection. The highest reagin titer is found in the second stage of syphilis, and later the titer gradually decreases – this allows the RPR to be used for monitoring treatment effectiveness.

It is important to know that the RPR test is not specific to syphilis only, so it may be falsely positive in other conditions: pregnancy, infections (e.g., Lyme disease, mononucleosis, toxoplasmosis), autoimmune diseases (collagenoses, vasculitis), or even after vaccination.

Test principle: The test is based on the detection of non-specific antibodies (reagins) that react with the cardiolipin antigen. Results are presented as reactive (positive) or non-reactive (negative), and in the case of a positive result, the titer is also indicated.

Recommendations:

• Recommended to be performed when syphilis is suspected or in cases of risky sexual contacts.
• Useful for monitoring treatment effectiveness – a decrease in titer indicates successful treatment.
• Used alongside specific tests (e.g., TPHA) to confirm diagnosis.
• May be applied during pregnancy, in cases of donation, or before surgeries.
• No specific preparation is required for the test, but the clinical context must be evaluated to rule out false-positive results.