IGRAs using early secretory antigenic target (ESAT)-6 and culture filtrate protein 10 kD (CFP-10) offer enhanced sensitivity and specificity by measuring IFNγ production in response to antigens more specific to M tuberculosis, and are not influenced by cross-reactivity to M bovis BCG and most NTM.7 However, there are limited data on the utility of IGRAs to diagnose M tuberculosis infection in persons from highly tuberculosis endemic settings. The two commercially available IGRAs include the ELISPOT-based T-SPOT.TB (Oxford Immunotec, UK) and the ELISA-based QuantiFERON TB Gold (Cellestis, Australia), with the in-tube form as the most recently available version, including TB 7.7 as an additional combined antigen. In the absence of a practical gold standard for M tuberculosis infection, exposure to an infectious tuberculosis index case has been used as a surrogate measure of infection and has been shown to correlate well with ELISPOT IFNγ responses in household contact and outbreak investigations.12 13 14 Direct comparisons of discordance between the two commercial IGRAs and the TST are limited, and there are few data on the comparison of both assays in relation to M tuberculosis exposure as a surrogate measure of infection and the influence of age.