The evaluation of whole blood cytokine assay for diagnosis of M.tuberculosis infection in South African children with household tuberculosis contact.
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Date
2019-04
Authors
Masilo, J. M.
Journal Title
Journal ISSN
Volume Title
Publisher
Vaal University of Technology
Abstract
Background: There are critical unmet needs for improved strategies in the detection
and diagnosis of M.tuberculosis infection in children, and for prevention of
tuberculosis disease in children. Bacillus Calmette-Guérin (BCG) vaccination has
limited the utility of tuberculin skin testing (TST) in areas with high vaccine coverage.
Objectives: The aim of this study was to estimate the prevalence of M.tuberculosis
infection in children with household tuberculosis contacts, using QFT-GIT testing in
comparison with TST.
Methods: This study was a cross-sectional design to assess the performance of a
new T-cell based blood test, namely QuantiFERON-TB Gold In Tube (QFT-GIT), for
diagnosis of tuberculosis infection in the children (n=182) of adults (n=124) with
pulmonary tuberculosis, additionally to determine the prevalence of M.tuberculosis
infection in children with household tuberculosis contacts, using QFT-GIT testing in
comparison with TST. The study was carried out at Chris Hani Hospital. For children
involved in the study, tuberculosis exposure information was obtained, together with
TST, QFT-GIT, and HIV testing.
Data obtained from both experiments was statistically analysed using SPSS version
24 to determine whether there was a significant agreement between QFT-GIT and
TST on the detection of M.tuberculosis prevalence in children with house hold
contacts with confirmed M.tuberculosis infection.
Results: This study examined the sensitivity and specificity of the QFT-GIT tests
compared with the standard TST for diagnosing latent tuberculosis disease in
paediatric contacts. Because of the lack of a latent tuberculosis “gold standard”, the
specificity and sensitivity of QFT-GIT was calculated with a two-by-two table method.
The specificity of the QFT-GIT was 84% and the sensitivity was 85%. There was a
good correlation between QFT-GIT and TST (Cohen’s kappa of 0.705). Seventeen
percent (17%) of the 182 children tested by QFT-GIT yielded indeterminate results.
Age was associated with indeterminate QFT-GIT results in paediatric tuberculosis
contacts. Point prevalence for QFT-GIT was recorded as 31% at baseline and 39.5%
after six months indicating variability between QFT-GIT results at baseline and after
six months.
Conclusion: It was concluded that the prevalence of tuberculosis infection was
common among South African children who live with an adult with active
tuberculosis. The agreement between QFT-GIT assay and TST for the diagnosis of
latent tuberculosis in children was high. Although TST and QFT-GIT assays
appeared comparable, QFT-GIT showed higher positivity rate amongst those
contacts with reported household tuberculosis exposure compared to TST. The QFTGIT
assay was a better indicator of the risk of M.tuberculosis infection than TST in a
BCG-vaccinated population.
Description
M. Tech. (Department of Biotechnology, Faculty of Applied and Computer Sciences), Vaal University of Technology.
Keywords
M.tuberculosis infection in children, Blood cytokine assay, Prevention of tuberculosis disease in children, Bacillus Calmette-Guérin (BCG), QFT-GIT assay, TST