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.
