Has Chlamydia trachomatis prevalence in young women in England, Scotland and Wales changed? Evidence from national probability surveys

Daphne-Zacharenia Kounali, Nicky Welton, Kate Soldan, Sarah C Woodhall, J Kevin Dunbar, Stephanie J Migchelsen, C Mercer, Paddy J Horner, Tony Ades

Research output: Contribution to journalArticle (Academic Journal)peer-review

2 Citations (Scopus)
215 Downloads (Pure)


We evaluate the utility of the National Surveys of Attitudes and Sexual Lifestyles (Natsal) undertaken in 2000 and 2010, before and after the introduction of the National Chlamydia Screening Programme, as an evidence source for estimating the change in prevalence of Chlamydia trachomatis (CT) in England, Scotland and Wales. Both the 2000 and 2010 surveys tested urine samples for CT by Nucleic Acid Amplification tests (NAATs). We examined the sources of uncertainty in estimates of CT prevalence change, including sample size and adjustments for test sensitivity and specificity, survey non-response, and informative non-response. In 2000, the unadjusted CT prevalence was 4.22% in women aged 18-24 years; in 2010, CT prevalence was 3.92%, a non-significant absolute difference of 0.30 percentage points (95% CrI -2.8 - 2.0). In addition to uncertainty due to small sample size, estimates were sensitive to specificity, survey non-response or informative non-response, such that plausible changes in any one of these would be enough to either reverse or double any likely change in prevalence. Alternative ways of monitoring changes in CT incidence and prevalence over time, are discussed.
Original languageEnglish
Article numbere107
Pages (from-to)e107
Number of pages7
JournalEpidemiology and Infection
Early online date4 Mar 2019
Publication statusPublished - 2019


  • chlamydia trachomatis
  • prevalence
  • sexually transmitted infections (STIs)

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