Was treatment for syphilis (Treponema pallidum infection) 20 years ago effective in a patient with reactive Treponema pallidum particle agglutination assay (TPPA) and non-reactive Rapid Plasma Reagin (RPR) test results?

From the Guidelines

The treatment for syphilis that the patient received 20 years ago appears to have been effective, as indicated by the reactive Treponema pallidum particle agglutination assay (TPPA) and non-reactive Rapid Plasma Reagin (RPR) test results, which is consistent with the "serofast state" expected in patients who have been successfully treated for syphilis in the past. The laboratory results show a reactive TPPA, which typically remains positive for life after effective treatment, as it detects antibodies specific to T. pallidum that persist regardless of treatment 1. However, the non-reactive RPR result indicates that the patient no longer has active infection, as non-treponemal tests like RPR usually become negative or show a significant decrease in titer after successful treatment 1.

The pattern of positive treponemal tests with negative non-treponemal tests is known as "serofast state" and is expected in patients who have been successfully treated for syphilis in the past 1. According to the 1998 guidelines for treatment of sexually transmitted diseases, most patients who have reactive treponemal tests will have reactive tests for the remainder of their lives, regardless of treatment or disease activity 1.

Some key points to consider in the management of syphilis include:

• The use of two types of serologic tests for syphilis: nontreponemal (e.g., RPR) and treponemal (e.g., TPPA) 1
• The expectation that nontreponemal test antibody titers will usually correlate with disease activity, and results should be reported quantitatively 1
• The possibility that nontreponemal antibodies can persist at a low titer for a long period, sometimes for the remainder of their lives, referred to as the serofast reaction 1
• The fact that treponemal test antibody titers correlate poorly with disease activity and should not be used to assess treatment response 1

No further treatment is needed unless there are new clinical symptoms or evidence of reinfection. The patient's current serological status is consistent with successfully treated syphilis, and the risk of morbidity, mortality, and impact on quality of life is minimal in this context.

From the FDA Drug Label

Therapy with penicillin G Potassium for Injection, USP may be indicated before results of such tests are known when there is reason to believe the infection may involve any of the organisms listed below, however, once these results become available, appropriate therapy should be continued Syphilis (congenital and neurosyphilis) Treponema pallidum

The patient was treated for syphilis 20 years ago, and the current Treponema pallidum particle agglutination assay (TPPA) is reactive, while the Rapid Plasma Reagin (RPR) test is non-reactive.

• The TPPA test is a treponemal test that typically remains positive for life after a Treponema pallidum infection.
• The RPR test is a non-treponemal test that can turn negative after successful treatment. Given this information, it can be inferred that the treatment for syphilis 20 years ago was likely effective, as the RPR test is non-reactive, indicating that the infection is no longer active 2.

From the Research

Effectiveness of Syphilis Treatment 20 Years Ago

• The effectiveness of syphilis treatment 20 years ago can be inferred from studies on the treatment of Treponema pallidum infection 3, 4, 5.
• According to a study published in 1990, penicillin has been used as first-line therapy in syphilis for more than 40 years, and T pallidum has not shown any signs of decreased sensitivity 3.
• The standard treatment at that time was depot preparations (benzathine penicillin and procaine penicillin) giving a continuous low penicillinaemia, and treatment failures in early syphilis were exceedingly rare 3.
• A study published in 2011 confirmed that a single dose of 2.4 million units of benzathine penicillin G remains the drug of choice for managing early syphilis, with reported treatment success rates of 90% to 100% 4, 5.

Interpretation of Test Results

• The patient's reactive Treponema pallidum particle agglutination assay (TPPA) and non-reactive Rapid Plasma Reagin (RPR) test results indicate that the patient has been infected with syphilis at some point, but the current disease activity is unclear 6.
• The RPR test is used to assess disease activity, and a non-reactive result may indicate that the patient has been successfully treated or that the disease is in a latent stage 3, 6.
• The TPPA test is a treponemal test that detects antibodies against Treponema pallidum and remains positive for life in most patients, even after successful treatment 6.

Treatment Outcome

• The treatment outcome for a patient with reactive TPPA and non-reactive RPR test results 20 years ago would depend on various factors, including the stage of the disease, the patient's immune status, and the effectiveness of the treatment regimen 3, 4, 5.
• According to a study published in 2015, patients with early syphilis who received a single dose of benzathine penicillin achieved rapid clearance of Treponema pallidum from blood and ulcer samples, with all patients achieving serologic cure 7.
• However, the study also noted that the treatment response may vary depending on the patient's immune status and the presence of co-infections, such as HIV 4, 5.