2.3. Latent TB Screening

Screening for LTBI was done with both tuberculin skin testing (TST) and interferon gamma release assay using the QuantiFERON TB gold method because all of our patients were vaccinated with BCG at birth. Plain X-ray chest was also done in all the patients at baseline along with detailed past history of tuberculosis infection and close contact with open TB cases. Either TST positive or IGRA positive was regarded as LTBI in this TST/IGRA combined method [6, 7]. Any doubtful finding was confirmed further with sputum examination and contrast enhanced chest computerized tomography. Sample for QuantiFERON assay was taken for each patient before administration of TST [3].