Factors Determining Serologic Response to Treatment in Patients with Syphilis

Background. The goal of this study was to describe the clinical and epidemiologic manifestations of a syphilis outbreak in downtown Madrid, Spain. Because human immunodeficiency virus (HIV)-positive patients may be at increased risk of serologic failure during syphilis treatment, analysis of factors determining the response to treatment was performed in a cohort of HIV-positive and HIV-negative patients with syphilis. Methods. We performed a longitudinal, retrospective study of patients with syphilis who received the diagnosis at a university-affiliated hospital in Madrid from 2003 through 2007. Results. Three hundred forty-seven cases of syphilis were identified and treated (30 primary, 164 secondary, 77 early latent, and 76 late cases of syphilis). Forty-one percent of patients were immigrants, mostly from South America and the Caribbean, and 49.3% were known to be HIV positive. Syphilis incidence increased from 15.6 to 35 cases per 100,000 person-years from 2003 to 2007. Most patients were men, and 50.4% were men who had sex with other men. Meningitis (4.9%) and uveitis (2.9%) were the complications most frequently observed, and their frequency did not differ between HIV-positive and HIV-negative patients. Serologic failure was observed in 44 (23.5%) patients: 37 (29.6%) of 125 HIV-positive patients and 7 (11.2%) of 62 HIV-negative patients (odds ratio, 3.3; 95% confidence interval, 1.38-7.93; P < .05). Men (hazard ratio [HR], 0.38), patients in the late stage of syphilis (HR, 0.46), and HIV-positive persons (HR, 0.61) demonstrated slower serological responses to treatment. HIV-negative patients responded more frequently to treatment, but after 2 years of follow-up, both groups shared similar response rates. Antiretroviral treatment reduced the time to serologic response (HR, 2.08; 95% confidence interval, 1.35-3.20; P < .001). Conclusion. Syphilis incidence rose 223% from 2003 to 2007, affecting mostly HIV-positive men, men who have sex with men, and immigrants. Men, patients in the late stages of syphilis, and HIV-positive persons may be at increased risk of serologic failure. Antiretroviral therapy significantly reduced the time to achieve response to syphilis treatment in HIV-positive patients.