Using chlamydia positivity to estimate prevalence: Evidence from the Chlamydia Screening Pilot in England

D. Scott LaMontagne*, Kevin Fenton, J. M. Pimenta, Mike Catchpole, P. A. Rogers, S. Randall, W. G. Hewitt, H. Mallinson, G. S. Underhill, L. McLean, T. Gleave, V. Harindra, A. K. Ghosh, J. M. Tobin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


Studies have suggested that positivity can be used to estimate the prevalence of Chlamydia trachomatis in large-scale chlamydia screening programmes. A recent pilot of opportunistic screening in England estimated that the prevalence among 16-24-year-old women in Portsmouth and Wirral was 9.8% and 11.2%, respectively. This study assessed the continued validity of positivity as an approximate for prevalence. We re-analysed data from the Chlamydia Screening Pilot to estimate positivity, calculated as total positive tests divided by total tests, and compared these estimates with the previously reported prevalence, measured as the number of women testing positive divided by the total number of women screened. Overall positivity was 9.4% in Portsmouth and 11.0% in the Wirral; these estimates were not statistically different from prevalence, regardless of health-care setting, age group or symptoms. We conclude that positivity can be used as a proxy for prevalence.

Original languageEnglish
Pages (from-to)323-327
Number of pages5
JournalInternational Journal of STD and AIDS
Issue number4
Publication statusPublished - Apr 2005

Bibliographical note

Copyright 2008 Elsevier B.V., All rights reserved.


  • Chlamydia
  • Chlamydia trachomatis
  • Positivity
  • Prevalence
  • Screening


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