Comparative analysis of tuberculin skin test and igra for detection of tuberculosis infection

Abstract

People with latent tuberculosis infection have no risk of disseminating infection and presents no clinical symptoms, however 5-10% of those who has infection has a risk of transiting into active tuberculosis during their lifetime. Thus we aimed to compare tuberculin skin test (TST) and interferon gamma release assay (IGRA) QuantiFERON®-TB Gold Plus (QFTPlus) and determine tuberculosis infection rate among household contacts (HHC) of tuberculosis patients. We recruited 280 HHC of the 204 tuberculosis index cases diagnosed between January to August 2017 at Tuberculosis dispensary, Khan-Uul district. We performed IGRA, TST and chest X-ray to study participants. The rate of tuberculosis infection was high, 57.1% (160/280) and 48.2% (135/280) by TST and QFT-Plus among HHC. Of the all participants, 71.4% (200/280) had chest X-ray and 75% (150/200) had abnormal outcome where 11 (7.3%) participants provided bacteriological test. Only 1 case (0.7%) turned out sputum smear positive. Poor concordance of the QFT-Plus and TST was observed with low Cohen kappa coefficient (0.38) with 68.9% agreement rate.