Prevalence of urogenital Chlamydia trachomatis increases significantly with level of urbanisation and suggests targeted screening approaches:: results from the first national population based study in the Netherlands

Objectives: Chlamydia trachomatis ( Chlamydia) is the most prevalent sexually transmitted bacterial infection and can cause considerable reproductive morbidity in women. Chlamydia screening programmes have been considered but policy recommendations are hampered by the lack of population based data. This paper describes the prevalence of Chlamydia in 15 - 29 year old women and men in rural and urban areas, as determined through systematic population based screening organised by the Municipal Public Health Services (MHS), and discusses the implications of this screening strategy for routine implementation. Methods: Stratified national probability survey according to "area address density'' (AAD). 21 000 randomly selected women and men in four regions, aged 15 - 29 years received a home sampling kit. Urine samples were returned by mail and tested by polymerase chain reaction (PCR). Treatment was via the general practitioner, STI clinic, or MHS clinic. Results: 41% ( 8383) responded by sending in urine and questionnaire. 11% ( 2227) returned a refusal card. Non-responders included both higher and lower risk categories. Chlamydia prevalence was significantly lower in rural areas (0.6%, 95% CI 0.1 to 1.1) compared with very highly urbanised areas ( 3.2%, 95% CI 2.4 to 4.0). Overall prevalence was 2.0% ( 95% CI 1.7 to 2.3): 2.5% ( 95% CI 2.0 to 3.0%) in women and 1.5% ( 95% CI 1.1 to 1.8) in men. Of all cases 91% were treated. Infection was associated with degree of urbanisation, ethnicity, number of sex partners, and symptoms. Conclusion: This large, population based study found very low prevalence in rural populations, suggesting that nationwide systematic screening is not indicated in the Netherlands and that targeted approaches are a better option. Further analysis of risk profiles will contribute to determine how selective screening can be done.