From the Guidelines
Retesting RPR titers after syphilis treatment should occur at 6,12, and 24 months, as recommended by the Centers for Disease Control and Prevention 1. This approach is based on the guidelines for sexually transmitted diseases treatment, which emphasize the importance of follow-up testing to assess treatment response and detect potential treatment failure.
- The first follow-up test should be performed at 6 months, with subsequent tests at 12 and 24 months, to monitor the decline in RPR titers.
- A successful treatment response is indicated by a fourfold decrease in titer (two dilutions) within 12-24 months of therapy 1.
- If titers fail to decline appropriately or if clinical symptoms persist, retreatment should be considered, and additional clinical and serologic follow-up is essential 1.
- HIV-positive patients may require more frequent monitoring, such as at 3,6,9,12, and 24 months, due to the potential for treatment failure or reinfection 1.
- It is also important to note that some patients, especially those treated for late syphilis, may maintain a low-positive titer indefinitely (known as a serofast state), which doesn't necessarily indicate treatment failure if the titer has appropriately decreased and stabilized 1.
From the Research
Retesting RPR Titer After Treatment
- The timing of retesting RPR titer after treatment is crucial in assessing the treatment response of syphilis patients 2.
- According to a study published in 2017, RPR titers were analyzed at 1,3,6,9, and 12 months among patients with an appropriate treatment response, and the results showed that the decline in RPR titers was ≥ 4-fold among 88.0% of participants at 3 months and ≥ 8-fold among 77.8% at 6 months 2.
- However, another study published in 2006 found that serological failure was defined as lack of a 4-fold drop in rapid plasma reagin titer 270-400 days after treatment, or a 4-fold increase in titer 30-400 days after therapy 3.
- A 2014 study compared the serological response to treatment for early syphilis with benzathine penicillin versus doxycycline or tetracycline, and the results showed that a statistically similar serological treatment success rate was observed in penicillin-treated patients (91.4%) when compared with patients treated with doxycycline/tetracycline (82.9%) 4.
- A 2022 study analyzed the serological treatment response to doxycycline versus benzathine penicillin in syphilis infections and found that doxycycline had a slightly lower, though not statistically different, success rate when compared with penicillin in treating primary syphilis, but appeared to have a reduced success rate in attaining resolution in late and undetermined syphilis infection 5.
- Another study published in 2012 evaluated RPR titer variation during the 14 days after therapy and found that about 20% of early syphilis patients had increases in RPR titers immediately after treatment, but these changes rarely influenced assessment of therapeutic outcome 6.
Factors Affecting RPR Titer Decline
- Male sex and baseline RPR titers ≤ 1:32 were associated with higher odds of seroreversion compared with females and titers > 1:32, respectively 2.
- The type of treatment used, such as doxycycline or benzathine penicillin, may also affect the RPR titer decline 3, 4, 5.
- The stage of syphilis, such as primary, secondary, or latent, may also influence the RPR titer decline 5, 6.