A new approach to estimating trends in chlamydia incidence

Ali, Hammad, Cameron, Ewan, Drovandi, Christopher C., McCaw, James M., Guy, Rebecca J., Middleton, Melanie, El-Hayek, Carol, Hocking, Jane S., Kaldor, John M., Donovan, Basil, & Wilson, David P. (2015) A new approach to estimating trends in chlamydia incidence. Sexually Transmitted Infections, 91, pp. 513-519.


View at publisher



Directly measuring disease incidence in a population is difficult and not feasible to do routinely. We describe the development and application of a new method of estimating at a population level the number of incident genital chlamydia infections, and the corresponding incidence rates, by age and sex using routine surveillance data.


A Bayesian statistical approach was developed to calibrate the parameters of a decision-pathway tree against national data on numbers of notifications and tests conducted (2001-2013). Independent beta probability density functions were adopted for priors on the time-independent parameters; the shape parameters of these beta distributions were chosen to match prior estimates sourced from peer-reviewed literature or expert opinion. To best facilitate the calibration, multivariate Gaussian priors on (the logistic transforms of) the time-dependent parameters were adopted, using the Matérn covariance function to favour changes over consecutive years and across adjacent age cohorts. The model outcomes were validated by comparing them with other independent empirical epidemiological measures i.e. prevalence and incidence as reported by other studies.


Model-based estimates suggest that the total number of people acquiring chlamydia per year in Australia has increased by ~120% over 12 years. Nationally, an estimated 356,000 people acquired chlamydia in 2013, which is 4.3 times the number of reported diagnoses. This corresponded to a chlamydia annual incidence estimate of 1.54% in 2013, increased from 0.81% in 2001 (~90% increase).


We developed a statistical method which uses routine surveillance (notifications and testing) data to produce estimates of the extent and trends in chlamydia incidence.

Impact and interest:

2 citations in Scopus
Search Google Scholar™
1 citations in Web of Science®

Citation counts are sourced monthly from Scopus and Web of Science® citation databases.

These databases contain citations from different subsets of available publications and different time periods and thus the citation count from each is usually different. Some works are not in either database and no count is displayed. Scopus includes citations from articles published in 1996 onwards, and Web of Science® generally from 1980 onwards.

Citations counts from the Google Scholar™ indexing service can be viewed at the linked Google Scholar™ search.

Full-text downloads:

25 since deposited on 09 Jan 2015
16 in the past twelve months

Full-text downloads displays the total number of times this work’s files (e.g., a PDF) have been downloaded from QUT ePrints as well as the number of downloads in the previous 365 days. The count includes downloads for all files if a work has more than one.

ID Code: 79932
Item Type: Journal Article
Refereed: Yes
Additional URLs:
Keywords: Incidence, chlamydia, Australia, epidemiology, disease notification, prevalence
DOI: 10.1136/sextrans-2014-051631
ISSN: 1472-3263
Divisions: Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2015 Authors.
Deposited On: 09 Jan 2015 05:30
Last Modified: 15 Nov 2015 08:36

Export: EndNote | Dublin Core | BibTeX

Repository Staff Only: item control page