IFNG and tuberculosis: Generally, there was a good correlation between IP-10 levels and IFNγ in the QFN test at baseline among the contacts (Spearman correlation, p-value) of 0.77, p <0.0001, and among the active TB cases (Spearman correlation of 0.63, p <0.0001) (S1 Fig) and this pattern was similar among the three groups: uninfected contacts, latently infected contacts, and the active TB cases (interaction p-value = 0.43).