Evaluation of interferon gamma release assay using Mycobacterium tuberculosis antigens for diagnosis of pulmonary tuberculosis in bcg vaccinated population of Kelantan, Malaysia
Although Malaysia is an intermediate tuberculosis (TB) burden country, the absolute number of new cases has been increasing recently. Improvement in early diagnosis followed by efficient chemotherapy is the major control strategy for TB. Currently, T-cell based interferon-gamma release assays usi...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2013
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| Subjects: | |
| Online Access: | http://eprints.usm.my/60858/1/HAJAR%20FAUZAN%20BIN%20AHMAD%20-%20e.pdf |
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| Summary: | Although Malaysia is an intermediate tuberculosis (TB) burden country, the
absolute number of new cases has been increasing recently. Improvement in early
diagnosis followed by efficient chemotherapy is the major control strategy for TB.
Currently, T-cell based interferon-gamma release assays using Mycobacterium
tuberculosis (MTB) antigens from QuantiFERON4-TB Gold In-Tube (QFT-GIT)
assays have shown unclear values in terms of sensitivity and specificity in the
diagnoses of active pulmonary and latent TB infections. For this study, two MTB
antigens known as VacIII and Ubi-VacIII were evaluated for their diagnostic
potential based on dynamic T-cell responses among BCG-vaccinated populations
were investigated. Thirty-six patients with active pulmonary TB and 38 healthy
controls (FIC) from a selected hospital in Kelantan, Malaysia were recruited and
tested by using gold standard assays and IGRA. The sensitivity and specificity of
QFT-GIT, VacIII and Ubi-VacIII antigens among BCG vaccinated population were
30.4% and 88.9%, 47.8% and 55.6%, and 30.4% and 18.5%, respectively. Even
though the overall agreement between IGRA and the gold standards assays showed
fairly poor correlation (K-values=0.320), the T-cell responses against the antigens
were considered statistically significant (/><0.001). In conclusion, all the 3 antigens
were unable to discriminate between TB and HC due to high variability of the
sensitivities and specificities they demonstrated. As compared to VacIII and Ubi-
VacIII, QFT-GIT showed better specificity however its low sensitivity was expected
due to the fact that the TB7.7 antigen is absent in clinical MTB strains of South East
Asia. |
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