When to Repeat Quantitative RPR After Syphilis Treatment
Repeat quantitative RPR testing at 6 and 12 months after treatment for primary and secondary syphilis, or at 6,12,18, and 24 months for latent syphilis, with HIV-infected patients requiring additional testing at 3 and 9 months. 1
Standard Follow-Up Schedule by Syphilis Stage
Primary and Secondary Syphilis
- Perform clinical and serological evaluation at 6 and 12 months after treatment 1
- Treatment success is defined as a fourfold (2 dilution) decrease in RPR titers (e.g., from 1:32 to 1:8) 1, 2
- This fourfold decline should occur within 6-12 months for early syphilis 2
Latent Syphilis
- Perform clinical and serological evaluation at 6,12,18, and 24 months after therapy 3, 1
- For late latent syphilis, the fourfold decline should occur within 12-24 months 2
- If nontreponemal titers fail to decline fourfold between 12 and 24 months, CSF examination should be performed and treatment administered accordingly 3
Intensive Monitoring for HIV-Infected Patients
HIV-infected patients require more frequent monitoring due to higher risk of treatment failure and atypical serologic responses. 2
Enhanced Schedule for HIV-Positive Patients
- For early syphilis (primary, secondary, early latent): Check RPR at 3,6,9,12, and 24 months 3, 2
- For late latent syphilis: Check RPR at 6,12,18, and 24 months 3, 2
- Some experts recommend CSF examination at 6 months post-treatment in HIV-infected patients, although benefit is unproven 3, 1
Treatment Failure Criteria in HIV-Infected Patients
- Failure to achieve a fourfold decrease in RPR titers by 6-12 months indicates treatment failure 3, 2
- Sustained fourfold increase in nontreponemal titer at any follow-up visit 2
- Persistent or recurrent clinical signs/symptoms 2
When to Intervene Based on RPR Results
Indications for CSF Examination and Retreatment
- Clinical symptoms develop or RPR titers increase fourfold at any time 1
- Nontreponemal test titers do not decrease fourfold within 6-12 months (for early syphilis) or 12-24 months (for late latent) 3
- In HIV-infected patients, strongly consider CSF examination and retreatment if titers do not decrease fourfold within the expected timeframe 3, 2
Retreatment Regimen
- Re-treat with benzathine penicillin G 7.2 million units (three weekly doses of 2.4 million units each) if CSF examination is normal 3, 2
Important Caveats and Common Pitfalls
The "Serofast" State
- Approximately 15-25% of adequately treated patients maintain persistently low RPR titers (1:1 to 1:4) 4
- This represents a serologic scar, not active infection, and does not require retreatment in the absence of clinical findings 4, 2
- Reinfection should be suspected only with a fourfold increase above the serofast baseline 2
Technical Considerations
- Always use the same nontreponemal test method (RPR vs VDRL) and preferably the same laboratory for serial monitoring, as RPR titers are often slightly higher than VDRL titers and cannot be directly compared 1, 2
- RPR titers may continue to increase for up to 2 weeks after treatment initiation, but this rarely affects outcome assessment 5