Objective: to assess the age- and sex-specific prevalence of Chlamydia trachomatis infection according to the indications for testing. This was done as part of a health technology assessment to identify the populations that would benefit most from universal screening, and to identify ongoing potential superfluous testing that could liberate resources to be used for targeted screening programs.
Methods: In Aarhus County, Denmark, population of 630,000, data were collected on 11,423 persons who were being tested for C. trachomatis (10,351 females and 1072 males). Indicated on the request slip were: the sex, the age and the reasons for testing (infected partner; planned transcervical procedure; symptoms consistent with C. trachomatis infection; or routine testing). All samples were analyzed by the Ligase Chain Reaction.
Results: More than 90% of all the tests were conducted in women. The majority of tests were performed in the 21-25 years age group but the prevalence was highest in the 16-20 years age group (7.2%; 95% CI: 5.4%-9.3%). A total of 25% of all tests were carried out in asymptomatic women above the age of 30 in whom the prevalence was only 1.3% (95% CI: 0.8%-1.9%). More than three times as many women (5.8%) than men (1.7%) were tested as sexual partners to C. trachomatis-infected index patients but the risk of infection was highest among men. In women who were tested prior to a transcervical procedure, the prevalence was highest (5.5%; 95% CI: 1.8%-12.4%) in the 16-20 years age group, whereas most samples were obtained in women aged 31-35 years in whom the prevalence was only 0.8% (0.2%-2.3%).
Conclusions: The prevalence of C. trachomatis infection justifies the screening of asymptomatic individuals below 30 years of age. At present, however, 25% of all tests are requested in asymptomatic women above the age of 30. It might be advisable to use the resources for systematic universal screening of younger individuals rather than to continue the current opportunistic screening of older women.