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We thank Ranganathan and colleagues1 for their insightful comments on our recent publication on QuantiFERON-TB Gold In Tube (QFT-G In Tube), an interferon-gamma release assay (IGRA), among children in India. 2 The comparison between their study3 on an earlier version of the QFT-G assay from a low prevalence setting, and our study2 from a high prevalence setting is indeed informative. To date, most studies on IGRAs have been conducted in low prevalence countries, and the few studies conducted in high incidence settings have reported findings that are somewhat inconsistent with the findings from studies in low incidence settings. 4 We suspect IGRA performance may vary across populations, depending on background disease prevalence and other factors such as HIV prevalence, malnutrition, BCG vaccination, non-tuberculous mycobacterial exposure, leprosy, helminthic and other tropical infections that can alter host immune responses. Therefore, more studies are needed in geographically diverse, tuberculosis endemic settings, with a special focus on patient or population subgroups most likely to benefit from the use of IGRAs. As discussed in our paper, the low rates of LTBI in our study were probably due to a combination of several factors:(1) the use of the 1 TU dosage of PPD RT23,(2) the high proportion of children with moderate to severe malnutrition,(3) the inclusion of hospitalized children with comorbid conditions, and (4) the inclusion of children with a lower risk of tuberculosis. The last factor was probably important because pediatricians in India tend to perform TST in children for a variety of indications, including …