An Evaluation of QuantiFERON-TB Gold in-Tube and Immunological Tests for TB Diagnosis in Iraqi Patients

Aims: Tuberculosis is an infectious disease caused by the bacillus Mycobacterium tuberculosis and other related species. It typically affects the lungs (pulmonary TB) but can affect other sites (extra-pulmonary TB). A profusion of articles have been published on the accuracy and uses of interferon-gamma releasing assays for detection of this disease.
Experimental Design: A prospective study.
Place and Duration of Study: This study was done in Kirkuk city between November 2012 to February 2013.
Methodology: The present study included 50 individuals (40 suspected tuberculosis patients and 10 healthy controls). The patient were examined for the presence of TB by using QuantiFERON-TB Gold In-Tube(QFT-GIT) assay, polymerase chain reaction (PCR) and compared them with certain new and routine tests like AFB smear, OnSite TB rapid test, erythrocyte sedimentation rate and chest X-ray.
Result: The present study showed a relation between QFT-GIT and OnSite TB rapid test, and they were positive in 25(86%) at the same time; QFT-GIT positive and OnSite TB rapid test were negative in 4(14%) of patients; QFT-GIT negative and OnSite TB rapid test positive were seen in 5(45%); while QFT-GIT and OnSiteTB rapid test were negative in 6(55%) of patients. In the control group only one QFT-GIT positive but it was OnSite TB test negative. 9(100%) of individuals for both tests were negative, 29 were males and 21 were females.
Conclusion: The study highlighted the sensitivity of IGRAs for diagnosis of active TB in combination with the rapid IgM/lgG tests for TB.The QFT assay appeared to be a more specific indicator of latent TB infection than TST. The association with blood groups and vaccination is also significant.