Serologic Response to Treatment in Syphilis

Serologic monitoring is the way to determine adequate treatment response, which is typically defined as a fourfold decline in Rapid Plasma Reagin (RPR) or Veneral Disease Research Laboratory (VDRL) titer within 6 months of treatment for patients with primary or secondary syphilis and within 12 months of treatment for patients with early latent syphilis. Studies documented close to 100% rate seroreversion 1 -2 years after penicillin treatment, depending on the stage of syphilis and duration of symptoms. HIV co-infection has several effects on the presentation, diagnosis, disease progression, and therapy of syphilis. Unusual syphilis serologic titers have been reported in HIV-infected patients, with either unexpected high or low titer, as well as delayed serologic response at the time of diagnosis. There are several studies concerned to syphilis serological treatment response comparing HIV-infected and HIV-negative patients. Some studies reported a slower serological response in HIV infected patients. A recent study showed that the use of high active antiretroviral therapy (HAART) and the routine use of macrolides for the prevention of opportunistic infections may reduce syphilis serologic failure rates among HIV-infected patients who have syphilis. Penicillin G, administered parenterally, is the preferred drug for treating all stages of syphilis (French et al., 2009; Workowski & Berman, 2010). Treatment failure can occur with any regimen. Assessing response to treatment frequently is difficult, and definitive criteria for cure or failure have not been established. According to the CDC guidelines recommendations, clinical and serologic evaluation should be performed 6 months and 12 months after treatment of patients with primary or secondary syphilis; more frequent evaluation might be prudent if follow-up is uncertain. Patients who have signs or symptoms that persists or recurs or who have sustained fourfold increase in nontreponemal test titer probably failed treatment or were reinfected. The latent syphilis is not transmitted sexually; the objective of treating patients with this stage of disease is to prevent complication. Quantitative nontreponemal serologic tests should be repeated at 6, 12, and 24 months for followup. Limited information is available concerning clinical and serological follow-up of patients who have tertiary syphilis. HIV-infected persons should be evaluated clinically and serologically for treatment failure at 3, 6, 9, 12, and 24 months after therapy (Workowski & Berman, 2010). Usually, treatment failure cannot be distinguished from reinfection with T. pallidum; in these cases a CSF analysis is recommended.