How do you diagnose repeat syphilis (Treponema pallidum) infection in someone who has been previously treated?

From the Guidelines

Diagnosing repeat syphilis infection in someone who has been previously treated requires monitoring for a fourfold or greater increase in nontreponemal test titers, such as RPR or VDRL, compared to the patient's baseline after treatment, along with new clinical signs or symptoms consistent with syphilis. This approach is necessary because previously treated patients typically maintain positive treponemal tests, like FTA-ABS or TP-PA, for life, making them less useful for diagnosing reinfection 1. When evaluating a patient with suspected repeat infection, it is essential to obtain a thorough sexual history and perform a complete physical examination looking for chancres, rashes, or other syphilis manifestations.

Some key points to consider in the diagnosis of repeat syphilis infection include:

• The use of both nontreponemal and treponemal tests, with the nontreponemal test result compared to previous titers 1
• A significant rise in titers suggests reinfection, especially when accompanied by new symptoms 1
• It is crucial to distinguish between reinfection and treatment failure, as management may differ 1
• Patients with confirmed reinfection should receive appropriate antibiotic therapy, typically benzathine penicillin G 2.4 million units IM in a single dose for early syphilis or weekly for three weeks for late or unknown duration syphilis 1

In terms of treatment, benzathine penicillin G 2.4 million units IM in a single dose for early syphilis or weekly for three weeks for late or unknown duration syphilis is the recommended antibiotic therapy for patients with confirmed reinfection. However, the management of repeat syphilis infection may vary depending on the specific circumstances of the patient, including the presence of HIV infection, which may increase the risk of treatment failure and neurologic complications 1.

Overall, diagnosing and managing repeat syphilis infection requires a comprehensive approach that includes clinical assessment, serological testing, and appropriate antibiotic therapy.