From the Guidelines
A reactive RPR with a titer of 1:1 and a positive treponemal antibody test in a patient with no history of syphilis likely indicates a past, treated syphilis infection rather than an active infection. Low RPR titers (1:1 to 1:4) typically suggest either very early infection, successfully treated past infection, or long-standing untreated infection 1. The positive treponemal antibody confirms exposure to Treponema pallidum at some point.
Key Considerations
- The patient's RPR titer of 1:1 is considered low and may not necessarily indicate active infection 1.
- Treponemal tests, such as the one used in this patient, typically remain positive for life after infection, regardless of treatment or disease activity 1.
- Non-treponemal tests like RPR may decrease over time but can persist at low titers even after successful treatment 1.
Clinical Approach
To determine if this represents active infection, additional clinical assessment is necessary, including:
- A complete physical examination looking for signs of primary, secondary, or tertiary syphilis.
- A detailed sexual history to assess recent exposure risk. If there's any suspicion of active infection or if the patient has no documented history of treatment, treatment with Benzathine penicillin G 2.4 million units IM as a single dose would be appropriate for presumed late latent syphilis. Follow-up testing in 6-12 months to ensure the RPR titer doesn't increase would be prudent to confirm the absence of active infection 1.
From the Research
Interpretation of Test Results
- A reactive RPR with a titer of 1:1, along with a positive treponema antibody test, may indicate a syphilis infection, but it is not definitive 2, 3.
- The RPR test is a non-treponemal test used to monitor syphilis activity, while treponemal tests, such as the treponema antibody test, are more specific for detecting the presence of Treponema pallidum antibodies 4, 2.
Active Infection vs. Past Infection
- A positive treponemal test can indicate either an active or past infection, as these antibodies can remain positive for life after an infection 5, 3.
- The RPR test can be used to assess disease activity, but a low titer of 1:1 may not necessarily indicate an active infection 2, 5.
Diagnostic Considerations
- The diagnosis of syphilis should be based on a combination of clinical presentation, laboratory test results, and medical history 5, 6.
- It is essential to consider the patient's medical history, including any previous syphilis infections or treatments, when interpreting test results 4, 3.
- Additional testing, such as a physical examination and review of medical history, may be necessary to determine the presence of an active syphilis infection 5, 6.