Adnan, Azree Syazril
(2006)
A pilot study on sensitivity and specificity of QuantiFERON-TB GOLD test on newly diagnosed mycobacterium tuberculosis infection in Kelantanese population.
Masters thesis, Universiti Sains Malaysia.
Abstract
Diagnosis of tuberculosis infection has not been simple, commonly diagnosis been made
after reviewing several investigation results. Unfortunately delay in diagnosis and hence
treatment has made tuberculosis infection not treated early. Therefore a new test with
reliability and rapidity is required. This study was carried out to compare between
QuantiFERON-TB GOLD test and sputum culture for the detection of active
Mycobacterium tuberculosis infection. Twenty four suspected active tuberculosis
infected patients enrolled in this pilot cross sectional study and each patient was required
to provide sputum and 5 mls of blood. _The T-cells from the patient's, serum were
stimulated in-vitro with antigens specific for M tuberculosis (ESAT -6 and CFP-10).
Hence, interferon gamma, (a cytokine that is released during tuberculosis infection) was
detected after the in-vitro stimulation and using the QuantiFERON-TB GOLD kit, the
level was quantified via ELISA method. It was analyzed using a computer software
provided by the Cellestis (Manufacturer of QuantiFERON-TB GOLD test).
Simultaneously sputum samples were obtained from the same patient and cultured for M
tuberculosis. The results showed that when compared to sputum Acid Fast Bacillii culture,
QuantiFERON-TB GOLD assay is 94.7 % sensitive and 80% specific, positive and
negative predicitive values of 94% and 80%. While the likelihood ratios were 4.73 for
positive cases and 16.7 for negative cases for M tuberculosis infection. Our study
suggests that QuantiFERON-TB GOLD assay is a useful diagnostic kit for diagnosis of
active tuberculosis infection in our country which is endemic for M tuberculosis infection
and in which most of the population had been vaccinated with BCG. The sensitivity
94.7% obtained in this study is high in comparison to other study carried out in Japan,USA and Australia in which each represents 89.5%, 91.3% and 83.3% (in pulmonary TB
cases). While the specificity of 80% in this study is considered low as compared to other
studies, 98.1% (Japan), 97.8% (Australia) and 99.8% (USA). The increasing numbers of
reported cases and delay in diagnosis due to delay in obtaining culture results are reasons
for carrying out this study. Delay in diagnosis has made tuberculosis difficult to eradicate
in our country. Therefore this study will provide evidence on the usefulness of
QuantiFERON-TB GOLD assay as a rapid diagnostic tool kit in diagnosing new
tuberculosis cases in our country. It will provide a useful supporting diagnostic
instrument to the clinician for fast and accurate result.
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