Durations of asymptomatic, symptomatic, and care-seeking phases of tuberculosis disease with a Bayesian analysis of prevalence survey and notification data

Ku, C.-C., MacPherson, P. , Khundi, M., Nzawa Soko, R. H., Feasey, H. R. A., Nliwasa, M., Horton, K. C., Corbett, E. L. and Dodd, P. J. (2021) Durations of asymptomatic, symptomatic, and care-seeking phases of tuberculosis disease with a Bayesian analysis of prevalence survey and notification data. BMC Medicine, 19, 298. (doi: 10.1186/s12916-021-02128-9) (PMID:34753468) (PMCID:PMC8579670)

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Abstract

Background: Ratios of bacteriologically positive tuberculosis (TB) prevalence to notification rates are used to characterise typical durations of TB disease. However, this ignores the clinical spectrum of tuberculosis disease and potentially long infectious periods with minimal or no symptoms prior to care-seeking. Methods: We developed novel statistical models to estimate progression from initial bacteriological positivity including smear conversion, symptom onset and initial care-seeking. Case-detection ratios, TB incidence, durations, and other parameters were estimated by fitting the model to tuberculosis prevalence survey and notification data (one subnational and 11 national datasets) within a Bayesian framework using Markov chain Monte Carlo methods. Results: Analysis across 11 national datasets found asymptomatic tuberculosis durations in the range 4–8 months for African countries; three countries in Asia (Cambodia, Lao PDR, and Philippines) showed longer durations of > 1 year. For the six countries with relevant data, care-seeking typically began half-way between symptom onset and notification. For Kenya and Blantyre, Malawi, individual-level data were available. The sex-specific durations of asymptomatic bacteriologically-positive tuberculosis were 9.0 months (95% credible interval [CrI]: 7.2–11.2) for men and 8.1 months (95% CrI: 6.2–10.3) for women in Kenya, and 4.9 months (95% CrI: 2.6–7.9) for men and 3.5 months (95% CrI: 1.3–6.2) for women in Blantyre. Age-stratified analysis of data for Kenya showed no strong age-dependence in durations. For Blantyre, HIV-stratified analysis estimated an asymptomatic duration of 1.3 months (95% CrI: 0.3–3.0) for HIV-positive people, shorter than the 8.5 months (95% CrI: 5.0–12.7) for HIV-negative people. Additionally, case-detection ratios were higher for people living with HIV than HIV-negative people (93% vs 71%). Conclusion: Asymptomatic TB disease typically lasts around 6 months. We found no evidence of age-dependence, but much shorter durations among people living with HIV, and longer durations in some Asian settings. To eradicate TB transmission, greater gains may be achieved by proactively screening people without symptoms through active case finding interventions

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:MacPherson, Professor Peter
Authors: Ku, C.-C., MacPherson, P., Khundi, M., Nzawa Soko, R. H., Feasey, H. R. A., Nliwasa, M., Horton, K. C., Corbett, E. L., and Dodd, P. J.
College/School:College of Medical Veterinary and Life Sciences > School of Health & Wellbeing > Public Health
Journal Name:BMC Medicine
Publisher:BioMed Central
ISSN:1741-7015
ISSN (Online):1741-7015
Copyright Holders:Copyright © 2021 The Authors
First Published:First published in BMC Medicine 19: 298
Publisher Policy:Reproduced under a Creative Commons License

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