IFNG and tuberculosis: The positive predictive value for incident disease (1·9 vs 0·9 for RISK11 compared with IFNγ release assay, respectively) was computed from the observed tuberculosis incidence rate, which was lower than that typically used in estimations (2%).3, 6 It is not possible to determine whether the late incident tuberculosis cases occurring among RISK11-negative participants were due to reactivation or new M tuberculosis infection.