What is the recommended approach for testing and treating syphilis?

Recommended Approach for Syphilis Testing and Treatment

The diagnosis of syphilis requires both treponemal and nontreponemal tests, as using only one type of test is insufficient for accurate diagnosis, and treatment should be with parenteral penicillin G, with the preparation, dosage, and length determined by disease stage. 1, 2

Diagnostic Testing Algorithm

• Darkfield microscopy or direct fluorescent antibody tests of lesion exudate are the definitive methods for diagnosing early syphilis when lesions are present 1
• Traditional algorithm: Screen with nontreponemal test (VDRL or RPR), followed by treponemal test confirmation (FTA-ABS, TP-PA) if reactive 2
• Alternative algorithm: Screen with treponemal-based enzyme immunoassay (EIA) or chemiluminescent immunoassay, followed by nontreponemal test for confirmation of active disease 2
• Both algorithms are effective, with recent studies showing no significant difference in diagnostic performance 3

Interpretation of Test Results

• Nontreponemal tests (VDRL, RPR) correlate with disease activity and should be reported quantitatively 2
• A fourfold change in titer (two dilutions) indicates a clinically significant difference in disease activity or treatment response 1, 2
• Treponemal tests (FTA-ABS, TP-PA) typically remain reactive for life regardless of treatment or disease activity 2
• False-positive nontreponemal tests can occur, especially in HIV-infected persons, requiring careful interpretation 2

Special Testing Considerations

• Sequential serologic tests should use the same testing method (VDRL or RPR) by the same laboratory 2
• VDRL and RPR titers cannot be directly compared as RPR titers are often slightly higher 2
• For suspected neurosyphilis, CSF examination is recommended, including VDRL-CSF, cell count, and protein 2
• CSF examination is also recommended for HIV-infected persons with late-latent syphilis or syphilis of unknown duration 2

Treatment Recommendations

• Parenteral penicillin G is the preferred drug for all stages of syphilis 2
• For early syphilis (primary, secondary, early latent): Benzathine penicillin G 2.4 million units IM as a single dose 4
• For late latent syphilis: Benzathine penicillin G 2.4 million units IM weekly for 3 weeks 4
• For neurosyphilis: Aqueous crystalline penicillin G 18-24 million units daily, administered as 3-4 million units IV every 4 hours for 10-14 days 2

Management of Special Populations

• All pregnant women should be screened for syphilis at the first prenatal visit, during the third trimester, and at delivery 4
• HIV-infected persons should be treated with the same regimens as those without HIV infection 2
• For penicillin-allergic patients who are not pregnant and do not have neurosyphilis, doxycycline is the recommended alternative 2
• Penicillin desensitization is recommended for pregnant women with penicillin allergy 2

Follow-up and Monitoring

• Clinical and serologic evaluation should be performed 6 and 12 months after treatment 2
• A fourfold decline in nontreponemal test titers indicates adequate treatment response 1
• Patients with persistent or recurrent signs/symptoms, or a sustained fourfold increase in titer, should be evaluated for treatment failure or reinfection 2

Common Pitfalls to Avoid

• Using only one type of test for diagnosis can lead to misdiagnosis 1, 5
• Failure to report nontreponemal test results quantitatively limits ability to monitor treatment response 1
• Comparing titers between different test types (VDRL vs. RPR) can lead to incorrect conclusions 2
• Relying on treponemal tests to assess treatment response is inappropriate as they typically remain positive for life 1
• Inadequate treatment or follow-up of sexual partners can lead to reinfection 2

By following this comprehensive approach to syphilis testing and treatment, clinicians can ensure accurate diagnosis, appropriate treatment, and effective monitoring to reduce morbidity and mortality associated with syphilis infection.