From the Guidelines
A positive treponema test with a negative RPR suggests a past, successfully treated syphilis infection or late/latent syphilis with low antibody titers, and for patients with this pattern and no documented prior treatment, I recommend treating for late latent syphilis with Benzathine penicillin G 2.4 million units IM weekly for 3 weeks. This pattern occurs because treponemal tests typically remain positive for life after infection, while non-treponemal tests like RPR may become negative after treatment or in late stages, as noted in a study from 1. For patients with this pattern, it is essential to determine if there was prior treatment, as retreatment may not be necessary if adequate therapy was previously completed, and clinical evaluation for neurosyphilis, cardiovascular syphilis, or gummatous lesions is important, especially in patients with HIV or other immunocompromising conditions. The sensitivity of non-treponemal tests like VDRL and RPR can vary depending on the stage of syphilis, with higher sensitivity in secondary syphilis and lower sensitivity in late latent syphilis, as shown in studies from 1 and 1. Follow-up testing is generally not needed after treatment for late latent syphilis unless symptoms develop or reinfection is suspected. Some key points to consider in the management of syphilis include:
- The use of treponemal tests, such as FTA-ABS or TP-PA, to confirm the diagnosis of syphilis
- The importance of determining the stage of syphilis, as this can impact treatment and management
- The need for clinical evaluation for neurosyphilis, cardiovascular syphilis, or gummatous lesions, especially in patients with HIV or other immunocompromising conditions
- The use of Benzathine penicillin G as the first-line treatment for late latent syphilis, with doxycycline as an alternative in cases of penicillin allergy.
From the Research
Treponema Reactive Presumptive, RPR Non-Reactive
- The patient's test results show a treponema reactive presumptive, but the RPR (Rapid Plasma Reagin) test is non-reactive 2, 3, 4, 5, 6.
- This combination of results can be seen in early syphilis, where the treponema test detects the presence of antibodies against the syphilis bacteria, but the RPR test has not yet become reactive 2, 4.
- The RPR test measures the level of antibodies against syphilis in the blood, and a non-reactive result can indicate that the infection is still in its early stages or that the patient has been treated successfully 3, 5.
- However, it is also possible that the patient has a false-negative RPR result, which can occur in some cases of syphilis, especially in patients with HIV 6.
Treatment and Management
- The treatment of choice for early syphilis is a single dose of 2.4 million units of benzathine penicillin G, which is effective in curing the infection in most cases 2, 3, 4, 5.
- Azithromycin is an alternative treatment option, but its use is limited by the emergence of resistance to the drug 4, 5.
- In patients with HIV, the treatment response to benzathine penicillin G may be poorer, and the addition of doxycycline to the treatment regimen may improve serologic outcomes 6.
Serologic Response
- The serologic response to treatment is an important indicator of the effectiveness of therapy, and a decline in RPR titers is expected after successful treatment 2, 3, 4, 5, 6.
- A 4-fold decline in RPR titers at 12 months after treatment is considered a satisfactory response to therapy 6.
- Factors that can influence the serologic response to treatment include the baseline RPR titer, the presence of HIV, and the use of adjunctive therapy such as doxycycline 6.