When should an RPR (Rapid Plasma Reagin) test be repeated after treatment for syphilis?

RPR Monitoring After Syphilis Treatment

RPR testing should be repeated at 3,6,9, and 12 months after treatment for early syphilis, and at 6,12, and 24 months for late syphilis to ensure adequate treatment response. 1

Monitoring Schedule by Syphilis Stage

Early Syphilis (Primary, Secondary, Early Latent)

• 3 months: First quantitative RPR test
• 6 months: Second quantitative RPR test with clinical evaluation
• 9 months: Third quantitative RPR test
• 12 months: Fourth quantitative RPR test with clinical evaluation

Late Syphilis (Late Latent, Tertiary)

• 6 months: First quantitative RPR test with clinical evaluation
• 12 months: Second quantitative RPR test with clinical evaluation
• 24 months: Final quantitative RPR test

HIV-Positive Patients

• More frequent monitoring is required: at 3,6,9,12, and 24 months after therapy 1

Expected Treatment Response

A successful treatment response is indicated by:

• ≥4-fold decline in RPR titer (e.g., from 1:32 to 1:8) within the first 3-6 months 1
• ≥8-fold decline by 6 months further confirms treatment success 1

It's important to note that despite appropriate treatment:

• Only 88% of patients achieve a ≥4-fold decline at 3 months 2
• Only 77.8% achieve a ≥8-fold decline at 6 months 2
• Complete seroreversion (negative RPR) occurs in only 9.6% at 6 months and 17.1% at 12 months 2

Risk Factors for Serological Failure

Be vigilant for serological failure in patients with:

• Baseline RPR titer ≤1:16 (3.9 times higher risk) 3
• Previous history of syphilis (3.1 times higher risk) 3
• CD4 count <350 cells/ml in HIV patients (2.4 times higher risk) 3
• Older age and multiple sex partners 4

Important Considerations

• Early fluctuations: About 20% of patients show a titer increase of at least 1 dilution in the first 14 days after therapy, particularly those with primary syphilis 5
• Serofast state: Some patients (21%) remain "serofast" with persistent low-level titers despite adequate treatment 4
• Treatment failure vs. reinfection: If titers fail to decline appropriately or increase after initial decline, consider:
  • Possible reinfection
  • HIV testing if status unknown
  • CSF examination to rule out neurosyphilis
  • Retreatment with benzathine penicillin G 1

Special Situations

• Neurosyphilis: Requires CSF examination every 6 months until cell count normalizes 1
• Pregnancy: More frequent monitoring may be needed; consult with specialists 1

Remember that while most patients will show serological improvement by 3-6 months, complete seroreversion is uncommon, and some patients will remain serofast despite adequate treatment 2, 4.