RESUMO
Introduction: Tuberculosis [TB] is an infectious disease affecting mostly the respiratory system with or without affection of other organ-systems caused mainly by infection with Mycobaterial tuberculosis [MTB]. However, not all cases of infection with any of the TB bacilli are converted to active or manifested infection and most cases are called latent tuberculosis infection [LTBI] which can be later on converted to active infection. There are several factors that underline the conversion from latent to active TB infections. Previously LTBIs was diagnosed by tuberculin skin testing [TST] but now there is new test formats which measures the released interferon-y [INF-y] after stimulation ofT-cells contained in whole patient blood by specific antigens obtained from MTB. These tests are called interferon gamma release assays [IGRAs] which are more sensitive and specific than TST one of these tests is the QuantiFERON-TB Gold In-Tube [QFT-G] which measures the released IFN-y by ELISA method
Aim of study: The aim of the current study was to compare the TST and QFT-G in diagnosing LTBIs in some groups of participants including TB contacts, HIVpatients, HCWs, prisoners in comparison to patients with active TB infection
Materials and methods: the study included 163 of close contacts to household TB cases, 32 healthcare workers in King Saud Chest hospital, 52 prisoners from Riyadh region, 25 HIVpatients, and 158 patients with active TB as a control group. History and general examination was done to all participants. Then TST was done using 2 IV by intradermal injection using Mantoux technique. Whole blood samples were taken for measuring the released interferon y using Quantiferon TB Gold In Tube [QFT-G] method
Results: TST was positive in 52.8% of TB contacts, 21.9% of HCWs, 34.6% of prisoners, 28% in HIV patients and in 97.5% of active TB patients, while QFT-G was positive in 56.4%, 12.5%, 57.7%, 24%, and 98.7% in previous groups respectively. The overall mean results for QFT-G [67%] were higher than that for TST [63.3%] with statistically insignificant results
Conclusion: QFT-G is more sensitive than TST in diagnosing LTBIs and further studies upon larger population number is need to investigate it specificity