Article Text

Download PDFPDF
What can be gained from comprehensive disaggregate surveillance? The Avon Surveillance System for Sexually Transmitted Infections
  1. Wendi Slater1,
  2. Katharine Sadler2,
  3. Jackie A Cassell2,
  4. Paddy Horner3,
  5. Nicola Low4
  1. 1South West Public Health Observatory, Grosvenor House, Bristol, UK
  2. 2Centre for Sexual Health and HIV Research, Department of Primary Care and Population Sciences, University College London, London, UK
  3. 3Milne Centre for Sexual Health, United Bristol Healthcare Trust, Bristol, UK
  4. 4Department of Social Medicine, University of Bristol, Bristol, UK
  1. Correspondence to:
 Dr N Low
 Department of Social and Preventive Medicine, University of Bern, Bern CH-3012, Switzerland; low{at}


Objective: To describe a new disaggregate surveillance system covering key diagnosed sexually transmitted infections in a UK locality.

Methods: The Avon System for Surveillance of Sexually Transmitted Infections (ASSIST) collects computerised person- and episode-based information about laboratory-diagnosed sexually transmitted infections from genitourinary medicine (GUM) clinics, the Avon Brook Clinic, and the Health Protection Agency and trust laboratories in primary care trusts in Avon. The features of the system are illustrated here, by describing chlamydia-testing patterns according to the source of test, age and sex, and by mapping the distribution of chlamydia across Bristol, UK.

Results: Between 2000 and 2004, there were 821 685 records of tests for sexually transmitted infections, with 23 542 positive results. The proportion of tests and positive results for chlamydia and gonorrhoea sent from general practice increased over time. Most chlamydia tests in both GUM and non-specialist settings were performed on women aged >25 years, but positivity rates were highest in women aged <25 years. The positivity rate remained stable between 2000 and 2004. Including data from all diagnostic settings, chlamydia rates were about twice as high as those estimated only from genitourinary clinic cases.

Conclusions: The ASSIST model could be a promising new tool for planning and measuring sexual health services in England if it can become sustainable and provide more timely data using fewer resources. Collecting denominator data and including infections diagnosed in primary care are essential for meaningful surveillance.

  • ASSIST, Avon Surveillance System for Sexually Transmitted Infections
  • GP, general practitioner
  • GUM, genitourinary medicine
  • NHS, National Health Service

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Competing interests: None declared.

  • WS established the data collection systems and database for ASSIST, conducted the first analyses and wrote the first draft. KS updated the analyses and contributed to revising the text. JC provided advice about national surveillance systems and contributed to revising the text. PH provided access to genitourinary clinic data, contributed to the development and establishment of ASSIST and contributed to revising the final draft. NL conceived the idea for ASSIST, contributed to its establishment, and revised the draft manuscript. All authors approved the final draft.