title: Screening for gonorrhoea using samples collected through the English national chlamydia screening programme and risk of false positives: a national survey of local authorities.
abstract: OBJECTIVE
  To investigate use of dual tests for Chlamydia trachomatis and Neisseria gonorrhoeae on samples collected through the National Chlamydia Screening Programme (NCSP) in England.
  
  
  METHODS
  During May-July 2013, we delivered an online survey to commissioners of sexual health services in the 152 upper-tier English Local Authorities (LAs) who were responsible for commissioning chlamydia screening in people aged 15-24 years.
  
  
  METHODS
  (1) The proportion of English LAs using dual tests on samples collected by the NCSP; (2) The estimated number of gonorrhoea tests and false positives from samples collected by the NCSP, calculated using national surveillance data on the number of chlamydia tests performed, assuming the gonorrhoea prevalence to range between 0.1% and 1%, and test sensitivity and specificity of 99.5%.
  
  
  RESULTS
  64% (98/152) of LAs responded to this national survey; over half (53% (52/98)) reported currently using dual tests in community settings. There was no significant difference between LAs using and not using dual tests by chlamydia positivity, chlamydia diagnosis rate or population screening coverage. Although positive gonorrhoea results were confirmed with supplementary tests in 93% (38/41) of LAs, this occurred after patients were notified about the initial positive result in 63% (26/41). Approximately 450-4500 confirmed gonorrhoea diagnoses and 2300 false-positive screens might occur through use of dual tests on NCSP samples each year. Under reasonable assumptions, the positive predictive value of the screening test is 17-67%.
  
  
  CONCLUSIONS
  Over half of English LAs already commission dual tests for samples collected by the NCSP. Gonorrhoea screening has been introduced alongside chlamydia screening in many low prevalence settings without a national evidence review or change of policy. We question the public health benefit here, and suggest that robust testing algorithms and clinical management pathways, together with rigorous evaluation, be implemented wherever dual tests are deployed.
authors.affiliation: Research Department of Infection and Population Health, University College London, London, UK.|Public Health England, National Centre for Infectious Disease Surveillance and Control (CIDSC), London, UK.
authors.forename: Nigel
authors.initials: N
authors.lastname: Field
authors.affiliation: Public Health England, National Centre for Infectious Disease Surveillance and Control (CIDSC), London, UK.
authors.forename: Iain
authors.initials: I
authors.lastname: Kennedy
authors.affiliation: Public Health England, National Centre for Infectious Disease Surveillance and Control (CIDSC), London, UK.
authors.forename: Kate
authors.initials: K
authors.lastname: Folkard
authors.affiliation: Public Health England, National Centre for Infectious Disease Surveillance and Control (CIDSC), London, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Duffell
authors.affiliation: Public Health England, National Centre for Infectious Disease Surveillance and Control (CIDSC), London, UK.
authors.forename: Katy
authors.initials: K
authors.lastname: Town
authors.affiliation: Sexually Transmitted Bacteria Reference Unit, Microbiological Services, Public Health England, London, UK.
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Ison
authors.affiliation: Public Health England, National Centre for Infectious Disease Surveillance and Control (CIDSC), London, UK.
authors.forename: Gwenda
authors.initials: G
authors.lastname: Hughes
mesh_terms: D000293:Adolescent; D002690:Chlamydia Infections / Q000175:diagnosis* / Q000453:epidemiology; D003625:Data Collection; D004739:England / Q000453:epidemiology; D005189:False Positive Reactions; D005260:Female; D006069:Gonorrhea / Q000175:diagnosis* / Q000453:epidemiology; D006801:Humans; D008297:Male; D008403:Mass Screening; D021141:Nucleic Acid Amplification Techniques; D015995:Prevalence; D012680:Sensitivity and Specificity; D013048:Specimen Handling; D055815:Young Adult
keywords: EPIDEMIOLOGY