Article Text

Estimating prevalence trends in adult gonorrhoea and syphilis in low- and middle-income countries with the Spectrum-STI model: results for Zimbabwe and Morocco from 1995 to 2016
  1. Eline L Korenromp1,
  2. Guy Mahiané2,
  3. Jane Rowley3,
  4. Nico Nagelkerke4,
  5. Laith Abu-Raddad5,
  6. Francis Ndowa6,
  7. Amina El-Kettani7,
  8. Houssine El-Rhilani8,
  9. Philippe Mayaud9,
  10. R Matthew Chico9,
  11. Carel Pretorius2,
  12. Kendall Hecht2,
  13. Teodora Wi10
  1. 1Avenir Health, Geneva, Switzerland
  2. 2Avenir Health, Glastonbury, Connecticut, USA
  3. 3London, UK
  4. 4Malawi-Liverpool Wellcome Trust, Blantyre, Malawi
  5. 5Weill Cornell Medical College—Qatar, Cornell University, Doha, Qatar
  6. 6Skin & Genito-Urinary Medicine Clinic, Harare, Zimbabwe
  7. 7Ministry of Health, Direction de l'Epidémiologie & Service de Maladies Sexuellement Transmissibles, Rabat, Morocco
  8. 8UNAIDS Morocco Country Office, Rabat, Morocco
  9. 9London School of Hygiene and Tropical Medicine, London, UK
  10. 10Department of Reproductive Health and Research, World Health Organization, Geneva, Switzerland
  1. Correspondence to Dr Eline L Korenromp, Avenir Health, 1 route de Morillons/150 Route de Ferney (WCC, office 164), PO Box 2100, Geneva 2 CH-1211, Switzerland; ekorenromp{at}


Objective To develop a tool for estimating national trends in adult prevalence of sexually transmitted infections by low- and middle-income countries, using standardised, routinely collected programme indicator data.

Methods The Spectrum-STI model fits time trends in the prevalence of active syphilis through logistic regression on prevalence data from antenatal clinic-based surveys, routine antenatal screening and general population surveys where available, weighting data by their national coverage and representativeness. Gonorrhoea prevalence was fitted as a moving average on population surveys (from the country, neighbouring countries and historic regional estimates), with trends informed additionally by urethral discharge case reports, where these were considered to have reasonably stable completeness. Prevalence data were adjusted for diagnostic test performance, high-risk populations not sampled, urban/rural and male/female prevalence ratios, using WHO's assumptions from latest global and regional-level estimations. Uncertainty intervals were obtained by bootstrap resampling.

Results Estimated syphilis prevalence (in men and women) declined from 1.9% (95% CI 1.1% to 3.4%) in 2000 to 1.5% (1.3% to 1.8%) in 2016 in Zimbabwe, and from 1.5% (0.76% to 1.9%) to 0.55% (0.30% to 0.93%) in Morocco. At these time points, gonorrhoea estimates for women aged 15–49 years were 2.5% (95% CI 1.1% to 4.6%) and 3.8% (1.8% to 6.7%) in Zimbabwe; and 0.6% (0.3% to 1.1%) and 0.36% (0.1% to 1.0%) in Morocco, with male gonorrhoea prevalences 14% lower than female prevalence.

Conclusions This epidemiological framework facilitates data review, validation and strategic analysis, prioritisation of data collection needs and surveillance strengthening by national experts. We estimated ongoing syphilis declines in both Zimbabwe and Morocco. For gonorrhoea, time trends were less certain, lacking recent population-based surveys.


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Supplementary materials

  • Abstract in French

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  • Abstract in Arabic

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  • Contributors ELK and TW conceived the project; ELK, GM and NN designed the Spectrum approach; GM, NN and CP designed the statistical methodology; ELK, GM, NN, LA-R, FN and JR analysed results; FN, JR, LA-R, PM, RMC, AE-K and HE-R provided country data; LAR, PM, RMC, FN and TW provided biomedical modelling assumptions; KH, GM and CP programmed the Spectrum user interface software; ELK and JR wrote the article; all authors analysed the final results, reached consensus in the interpretation and contributed to writing the final article.

  • Funding The project was funded by the WHO, Department of Reproductive Health and Research. LA-R acknowledges the support of Qatar National Research Fund (NPRP 9-040-3-008), which provided the main funding for generating the data provided for this study.

  • Competing interests None declared.

  • Provenance and peer review Commissioned; externally peer reviewed.

  • More info The views expressed in this paper are those of the authors and do not necessarily represent the position of Avenir Health, the WHO, the Joint United Nations Programme on HIV and AIDS, Morocco's Ministry of Health or any other affiliated organisation.

  • Data sharing statement All data used were provided within the manuscript and its three supplementary files.

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