Coverage is the key for effective screening of Chlamydia trachomatis in Australia

Background. The rate of diagnosis of Chlamydia trachomatis (chlamydia) infection has risen dramatically in Australia. In response, the Australian government is planning to implement systematic screening and testing. Several decisions must be made, including whom to screen. Methods. To inform decisions surrounding screening, a dynamic transmission model of the chlamydia epidemic was developed and parameterized with Australian sexual behavior and epidemiology data. A range of screening strategies and coverage rates were evaluated targeting various groups based on age and sex. Rigorous uncertainty and sensitivity analyses were undertaken. Results. The model predicts that even moderate screening coverage in young adults (< 25 years old) will reduce prevalence rapidly. The absolute numbers of people screened, rather than the sex targeted, is the key determinant in reducing prevalence. Sensitivity analysis determined that chlamydia transmission is strongly related to 2 biological parameters (the proportion of infections that are asymptomatic in women and the duration of infection in men) and 2 behavioral parameters (the frequency of sex acts for 20-24-year-olds and the level of condom usage). Conclusions. The model predicts that routine annual screening can significantly reduce the prevalence of chlamydia within 10 years, provided that adequate screening coverage is achieved. The most effective screening strategies will be those that target 20-24-year-olds.