Our findings indicate that measuring IFN-γ responses might be helpful in predicting active TB weeks to months earlier than current diagnostic algorithms (which rely on follow-up skin testing of contacts who were initially skin test negative 8–10 weeks after exposure) [34] and in identifying which exposed contacts have been infected with M. tuberculosis, but cannot identify which contacts with latent TB infection will subsequently develop TB. This evidence concerns the gene IFNG and tuberculosis.