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Original research
Population-level diagnosis and care cascade for chlamydia in Australia
  1. Richard T Gray1,
  2. Denton Callander1,2,
  3. Jane S Hocking3,
  4. Skye McGregor1,
  5. Hamish McManus1,
  6. Amalie Dyda4,
  7. Clarissa Moreira5,
  8. Sabine Braat3,
  9. Belinda Hengel6,
  10. James Ward7,
  11. David P Wilson5,
  12. Basil Donovan1,8,
  13. John M Kaldor1,
  14. Rebecca J Guy1
  1. 1 The Kirby Institute, Faculty of Medicine, UNSW Sydney, Kensington, New South Wales, Australia
  2. 2 NYU Spatial Epidemiology Lab, School of Medicine, New York University, New York, NY, USA
  3. 3 Melbourne School of Population and Global Health, University of Melbourne, Carlton, Victoria, Australia
  4. 4 Faculty of Medicine, Kirby Institute, Sydney, New South Wales, Australia
  5. 5 The Burnett Institute, Melbourne, Victoria, Australia
  6. 6 Apunipima Cape York Health Council, Cairns, Queensland, Australia
  7. 7 Infectious Diseases Research, South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia
  8. 8 Sydney Sexual Health Centre, Sydney, New South Wales, Australia
  1. Correspondence to Dr Richard T Gray, The Kirby Institute, Faculty of Medicine, UNSW Sydney, Kensington, NSW 2052, Australia; Rgray{at}


Objectives Key strategies to control chlamydia include testing, treatment, partner management and re-testing. We developed a diagnosis and care cascade for chlamydia to highlight gaps in control strategies nationally and to inform efforts to optimise control programmes.

Methods The Australian Chlamydia Cascade was organised into four steps: (1) annual number of new chlamydia infections (including re-infections); (2) annual number of chlamydia diagnoses; (3) annual number of diagnoses treated; (4) annual number of diagnoses followed by a re-test for chlamydia within 42–180 days of diagnosis. For 2016, we estimated the number of infections among young men and women aged 15–29 years in each of these steps using a combination of mathematical modelling, national notification data, sentinel surveillance data and previous research studies.

Results Among young people in Australia, there were an estimated 248 580 (range, 240 690–256 470) new chlamydia infections in 2016 (96 470 in women; 152 100 in men) of which 70 164 were diagnosed (28.2% overall: women 43.4%, men 18.6%). Of the chlamydia infections diagnosed, 65 490 (range, 59 640–70 160) were treated (93.3% across all populations), but only 11 330 (range, 7660–16 285) diagnoses were followed by a re-test within 42–180 days (17.3% overall: women 20.6%, men 12.5%) of diagnosis.

Conclusions The greatest gaps in the Australian Chlamydia Cascade for young people were in the diagnosis and re-testing steps, with 72% of infections undiagnosed and 83% of those diagnosed not re-tested: both were especially low among men. Treatment rates were also lower than recommended by guidelines. Our cascade highlights the need for enhanced strategies to improve treatment and re-testing coverage such as short message service reminders, point-of-care and postal test kits.

  • high-income setting
  • care cascade
  • genital chlamydia trachomatis
  • surveillance and monitoring
  • sti guidelines
  • incidence
  • control

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  • Handling editor Nicola Low

  • Collaborators Australian STI Diagnosis and Care Cascade Reference Group (listed under Acknowledgements).

  • Contributors Conceptualisation: RTG, SM, DPW, BD, JW, JMK, RJG. Provision of ACCEPt data: SB, JSH. Provision of ACCESS data: DC, AD, CM, RJG. Provision of other data: SM, HM, JW. Coding and code repository: RTG. Analysis: RTG, DC. Validation: JHS, SM, AD, CM, SB, BH, JW. Visualisation: RTG. Writing—original draft: RTG, DC. Writing—review and editing: all authors.

  • Funding The Kirby Institute is funded by the Australian Government Department of Health and is affiliated with the Faculty of Medicine, UNSW Sydney, Australia.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available in a public, open-access repository.