A population-based study of infectious syphilis rediagnosis in British Columbia, 1995-2005.

BACKGROUND: The Canadian province of British Columbia has experienced an ongoing heterosexual infectious syphilis epidemic since July 1997. In this study, we sought to characterize individuals who received a diagnosis of syphilis more than once in a cohort of reported cases from 1995 through 2005 in British Columbia.
METHODS: Data for all cases of primary, secondary, and early latent syphilis from 1 January 1995 through 31 December 2005 were extracted from the British Columbia Provincial Sexually Transmitted Disease Surveillance Database. A descriptive analysis was conducted on all variables from the cases, and the incidence density of syphilis rediagnosis was calculated. Bivariate and multivariate analyses were conducted using Cox proportional hazards regression techniques to compare those who received a syphilis diagnosis once with those who received a syphilis diagnosis more than once within the 10-year period.
RESULTS: By 2006, up to 10% of new cases of syphilis in the province were attributed to individuals who had received a previous diagnosis of syphilis within the preceding 10 years. In Cox proportional hazards regression analysis, individuals with the following characteristics were associated with an increased risk of becoming reinfected with syphilis: human immunodeficiency virus seropositivity, history of ever having gonorrhea or chlamydia, aboriginal ethnicity, and being a man who had sex with men.
CONCLUSIONS: In this study, an increasing proportion of syphilis cases in British Columbia were attributed to a rediagnosis during the previous decade. Individuals with syphilis rediagnosis may represent a core group of transmitters who continue to engage in risky behavior and sustain the epidemic. Policies for prevention need to better consider the role of interventions to decrease rates of repeat diagnoses of sexually transmitted infections.