Age at first episode of venereal syphilis in an Aboriginal population: an application of survival analysis

Objective: To identify the age at which screening for syphilis could be ceased in Kimberley Aboriginal people who had remained seronegative and whether this age was the same for people with and without a past history of gonorrhea.Design: Retrospective cohort study.Setting: The Kimberley region in the far north of Western Australia.Participants: Kimberley Aboriginal residents.Main Outcome Measure: Age at seroconversion.Results: Survival analysis showed that seroconversion due to venereal syphilis occurred largely during the years between the late teens and early 20s. The probability of seroconverting by a given age was related to the time at which the subject's last gonorrhea infection occurred.Conclusions: As a result of this study, annual periodic screening for syphilis is now offered to Kimberley Aboriginal people only between the ages of 15 and 25 years, allowing for the redistribution of resources to other activities that have greater potential to decrease the incidence of all STDs.