Prevalence of latent tuberculosis using the tuberculin skin test in two human immunodeficiency virus endemic municipalities in South Africa (2016 – 2018)
Date
2019
Authors
Murphy, Williams Victor
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Abstract
Background: Tuberculosis is a global health threat and a leading cause of mortality in low and middle-income countries of Africa, Asia and Western Pacific responsible for about 1.6 million deaths in 2017. In South Africa, it is the highest cause of mortality. This is compounded by the high HIV prevalence which has been noted to be the leading cause of immunosuppression leading to reactivation of latent tuberculosis to active tuberculosis disease.
Methods: The research adopted a cross-sectional study design approach. This was in the form of secondary analysis of baseline data from a completed cohort study (PHIRST Study: 2016 - 2018) to determine transmission dynamics of infectious respiratory conditions including tuberculosis. The Analysis included determination of prevalence of latent tuberculosis infection at two sites - Agincourt and Klerksdorp using TST, and annual risk of tuberculosis infection. A Logistic and multi-level analysis was used to predict risk factors for latent tuberculosis infection both at the individual and household level.
Results: The overall prevalence of TST-positive was 20.5%. Prevalence was higher at Klerksdorp (24.3 %) compared to Agincourt (16.3%) and it increased with increase in age. A prevalence of 1.9 - 45% was seen in Agincourt and 5.3 - 51.9% in Klerksdorp. The lowest prevalence was seen in <5 age group and the highest in the 41-45 age group at both sites. A significant association was seen between HIV status and TST-positive prevalence (OR=1.63; 95% CI: 1.13, 2.35, p=0.009) but this became insignificant after controlling for age and sex (OR=1.12; 95% CI: 0.76, 1.65; p=0.567). Overall household prevalence was 54.2% with Klerksdorp having a higher household prevalence of 70.5% and Agincourt 36%. The annual risk of TB infection (ARTI) was 3.8% in participants aged ≤15 years and underfive age group had the highest value. ARTI reduced with increase in age, higher in males and in those with negative and unknown HIV status. Individual risk factors for latent TB infection were being a resident of Klerksdorp and increasing age. HIV status, past TB history, sex, and BMI were not significant risk factors for TST-positivity. At the household level, the number of windows, smoking within households and wealth index were significant predictors of latent TB infection.
Conclusion: Prevalence of TST-positivity is higher in Klerksdorp both at the individual and household level compared to Agincourt. Younger age was associated with a higher risk of TB infection and the risk of infection decreased with increase in age. Increasing age, living in Klerksdorp, number of windows in a house, smoking within households and wealth index significantly predicted TST-positivity.
Description
A research report submitted in partial fulfillment of the requirements for the degree of Master of Science in Epidemiology in the field of Epidemiology and Biostatistics to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, 2019