When to recheck Rapid Plasma Reagin (RPR) test after treating for syphilis?

From the Guidelines

RPR testing should be rechecked at 6 and 12 months after treatment for syphilis to confirm adequate response, as recommended by the Centers for Disease Control and Prevention 1.

Key Considerations

• The primary goal of rechecking RPR is to assess treatment response and detect potential treatment failure or reinfection.
• A fourfold decrease in RPR titer within 6-12 months after therapy is indicative of a successful response 1.
• Patients with HIV or those treated for late latent syphilis may require more frequent evaluation, at 3-month intervals instead of 6-month intervals 1.
• If additional follow-up cannot be ensured, re-treatment is recommended to prevent potential complications 1.

Special Considerations

• More frequent monitoring may be needed for patients with neurosyphilis, tertiary syphilis, or during pregnancy.
• The RPR test remains reactive in many patients despite successful treatment, known as serofast state, but the titer should still show significant decline.
• Failure of nontreponemal test titers to decline fourfold within 6 months after therapy is indicative of probable treatment failure, and CSF examination and retreatment may be necessary 1.

From the Research

Rechecking RPR after Treating for Syphilis

• The timing for rechecking RPR (Rapid Plasma Reagin) after treating for syphilis can vary depending on several factors, including the stage of the disease and the patient's response to treatment 2.
• According to the study by 3, serological response to therapy was evaluated at 3,6,9, and 12 months following therapy, and participants whose RPR test became nonreactive or whose RPR titer decreased ≥2 dilutions were classified as responding to therapy.
• Another study by 4 defined serological failure as lack of a 4-fold drop in RPR titer 270-400 days after treatment, or a 4-fold increase in titer 30-400 days after therapy.
• The study by 5 defined cure as a decline in the RPR titer of at least two dilutions by nine months after treatment.
• A more recent study by 2 suggests that in persons with early syphilis who do not achieve a ≥4-fold serologic decline in their RPR titers 6-12 months after adequate therapy, CSF examination should be considered.
• Additionally, the study by 6 compared the treatment responses to single-dose benzathine penicillin G combined with 7-day doxycycline versus benzathine penicillin G alone in people with HIV, and found that the combination therapy achieved higher serologic responses at 12 months, with a serologic response rate of 79.5% compared to 70.3% for benzathine penicillin G alone.

Factors Affecting RPR Recheck Timing

• The stage of syphilis, with early syphilis requiring more frequent monitoring 3, 4.
• The patient's HIV status, with HIV-infected individuals potentially requiring more frequent monitoring 2, 6.
• The patient's response to treatment, with those who do not achieve a ≥4-fold serologic decline in their RPR titers 6-12 months after adequate therapy requiring further evaluation 2.