Predictors of serofast state after treatment for early syphilis in HIV-infected patients.

Abstract

Non-treponemal serological tests are used to monitor treatment response during syphilis infection. Syphilis- and HIV-coinfected patients may experience incomplete resolution in non-treponemal titres, which is referred to as the serofast state. The goal of this study was to evaluate risk factors for serofast state in HIV-infected patients. From November 2015 to June 2018, 1530 HIV-positive patients were tested for syphilis using a Treponema pallidum particle agglutination (TPPA) assay. Among TPPA-positive patients, medical records were reviewed for early syphilis infection. Serofast state was defined as a less than four-fold decrease in non-treponemal antibody titres during a 6-month follow-up period in the absence of symptoms of syphilis. Baseline characteristics were tested as predictive factors of serological response. In all, 515 patients (33.7%) tested positive in TPPA assays, and in 163 patients at least one previous syphilis infection was documented. A total of 61 out of 163 patients (37.4%) were in a serofast state. A history of previous syphilis infection (61 vs. 43%; P=0.04) was more common in serofast patients than in patients with serological cure after 6months. Non-treponemal titres ≥1:32 before therapy (47 vs. 25%; P=0.005) and adjunctive corticosteroids to prevent the Jarisch-Herxheimer reaction (35% vs 15%; P=0.006) were associated with serological cure after 6months, but corticosteroid therapy had no influence at 12months. The intensity of syphilis treatment did not affect serological cure. Corticosteroids for prevention of the Jarisch-Herxheimer reaction were associated with earlier serological cure. Although serological response is the accredited surrogate method to monitor syphilis treatment, the biological significance of the serofast state remains unclear.