TST and infection: Whereas those HHC with 1st TST positive may be a heterogeneous group, potentially including individuals with longstanding Mtb infection (unrelated to the index case exposure) and/or BCG cross-reactive individuals in addition to recent infection (unobserved TST converters), IGRA identified 82% of these individuals (Figure 1D), a significantly greater percentage compared to TST converters (p<0.001).