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Randomised controlled trial of screening for Chlamydia trachomatis to prevent pelvic inflammatory disease: the POPI (prevention of pelvic infection) trial

BMJ 2010; 340 doi: (Published 08 April 2010) Cite this as: BMJ 2010;340:c1642
  1. Pippa Oakeshott, reader in general practice1,
  2. Sally Kerry, senior lecturer in medical statistics1,
  3. Adamma Aghaizu, research assistant1,
  4. Helen Atherton, doctoral student2,
  5. Sima Hay, lecturer in midwifery3,
  6. David Taylor-Robinson, professor emeritus4,
  7. Ian Simms, epidemiologist5,
  8. Phillip Hay, reader in genitourinary medicine6
  1. 1Division of Community Health Sciences, St George’s, University of London SW17 0RE
  2. 2Department of Primary Care and Social Medicine, Imperial College, London
  3. 3Florence Nightingale School of Nursing and Midwifery, King’s College, London
  4. 4Division of Medicine, Imperial College London, St Mary’s Campus
  5. 5Health Protection Agency, Centre for Infections, London
  6. 6Department of Genitourinary Medicine, St George’s Hospital, London
  1. Correspondence to: P Oakeshott oakeshot{at}
  • Accepted 16 February 2010


Objective To determine whether screening and treating women for chlamydial infection reduces the incidence of pelvic inflammatory disease over the subsequent 12 months.

Design Randomised controlled trial.

Setting Common rooms, lecture theatres, and student bars at universities and further education colleges in London.

Participants 2529 sexually active female students, mean age 21 years (range 16-27).

Intervention Participants completed a questionnaire and provided self taken vaginal swabs, with follow-up after one year. Samples were randomly allocated to immediate testing and treatment for chlamydial infection, or storage and analysis after a year (deferred screening controls).

Main outcome measure Incidence of clinical pelvic inflammatory disease over 12 months.

Results Baseline prevalence of chlamydia was 5.4% (68/1254) in screened women and 5.9% (75/1265) in controls. 94% (2377/2529) of women were followed up after 12 months. The incidence of pelvic inflammatory disease was 1.3% (15/1191) in screened women compared with 1.9% (23/1186) in controls (relative risk 0.65, 95% confidence interval 0.34 to 1.22). Seven of 74 control women (9.5%, 95% confidence interval 4.7% to 18.3%) who tested positive for chlamydial infection at baseline developed pelvic inflammatory disease over 12 months compared with one of 63 (1.6%) screened women (relative risk 0.17, 0.03 to 1.01). However, most episodes of pelvic inflammatory disease occurred in women who tested negative for chlamydia at baseline (79%, 30/38). 22% (527/2377) of women reported being tested independently for chlamydia during the trial.

Conclusion Although some evidence suggests that screening for chlamydia reduces rates of pelvic inflammatory disease, especially in women with chlamydial infection at baseline, the effectiveness of a single chlamydia test in preventing pelvic inflammatory disease over 12 months may have been overestimated.

Trial registration NCT00115388.


  • We thank the students and staff at London Southbank University; Kingston University; City University; St George’s, University of London; Roehampton University; London College of Fashion; London College of Communication; University of East London; Greenwich University; University of Westminster; Wimbledon School of Art; Kingston College; Lambeth College; Southwark College; South Thames College; Lewisham College; Bromley College; North East Surrey College of Technology; Carshalton College; Merton College; Coulsdon College; and Croydon College. We also thank research assistants Deborah Banks, Ruth Harbit, and Stella Ivaz; research nurses Sally Dean and Cathy McKay; peer recruiters Linzie Long, Michelle Lamb, Laura Proctor, Sarah Simms, Sarah Kerry, and Sheila Kerry, and grant administrator Frances Kazakos. We also thank Drs Harry Mallinson and Jorgen Jensen for doing the chlamydia tests; Drs Elizabeth Williams, Katia Prime, and Paddy Horner for analysing the data on pelvic inflammatory disease; and the staff at the general practices, genitourinary medicine clinics, sexual health clinics, and hospitals who provided copies of medical records.

  • Contributors. PEH, PO, and SK conceived and designed the study. All authors helped draft and revise the article and approved the final version to be published. PO and SK are guarantors.

  • Funding: This study was supported by the BUPA Foundation (grant No 684/GB14B). TMA sample collecting kits were provided by Gen-Probe (San Diego, CA).

  • Competing interests: All authors have completed the unified competing interest form at (available on request from the corresponding author) and declare (1) no financial support for the submitted work from anyone other than their employer; (2) no financial relationships with commercial entities that might have an interest in the submitted work; (3) no spouses, partners, or children with relationships with commercial entities that might have an interest in the submitted work; and (4) no non-financial interests that may be relevant to the submitted work.

  • Ethical approval: This study was approved by Wandsworth research ethics committee (reference 03.0012).

  • Data sharing: No additional data available.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: and

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