Estimating local chlamydia incidence and prevalence using surveillance data

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Title: Estimating local chlamydia incidence and prevalence using surveillance data
Author(s): Lewis, J
White, PJ
Item Type: Journal Article
Abstract: Background: Understanding patterns of chlamydia prevalence is important for addressing inequalities and planning cost-effective control programs. Population-based surveys are costly; the best data for England come from the Natsal national surveys which are only available once per decade, and are nationally representative but not powered to compare prevalence in different localities. Prevalence estimates at finer spatial and temporal scales are required. Methods: We present a method for estimating local prevalence by modeling the infection, testing and treatment processes. Prior probability distributions for parameters describing natural history and treatment-seeking behavior are informed by the literature or calibrated using national prevalence estimates. By combining them with surveillance data on numbers of chlamydia tests and diagnoses, we obtain estimates of local screening rates, incidence and prevalence. We illustrate the method by application to data from England. Results: Our estimates of national prevalence by age group agree with the Natsal-3 survey. They could be improved by additional information on the number of diagnosed cases that were asymptomatic. There is substantial local-level variation in prevalence, with more infection in deprived areas. Incidence in each sex is strongly correlated with prevalence in the other. Importantly, we find that positivity (the proportion of tests which were positive) does not provide a reliable proxy for prevalence. Conclusion: This approach provides local chlamydia prevalence estimates from surveillance data, which could inform analyses to identify and understand local prevalence patterns and assess local programs. Estimates could be more accurate if surveillance systems recorded additional information, including on symptoms.
Publication Date: 1-Jul-2017
Date of Acceptance: 3-Sep-2016
ISSN: 1531-5487
Publisher: Lippincott, Williams and Wilkins
Start Page: 492
End Page: 502
Journal / Book Title: Epidemiology
Volume: 28
Issue: 4
Copyright Statement: © 2017 The Author(s). Published by Wolters Kluwer Health, Inc. This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Sponsor/Funder: Medical Research Council (MRC)
Funder's Grant Number: MR/K010174/1B
Keywords: Science & Technology
Life Sciences & Biomedicine
Public, Environmental & Occupational Health
0104 Statistics
1117 Public Health And Health Services
Publication Status: Published
Appears in Collections:Faculty of Medicine
Epidemiology, Public Health and Primary Care

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