Table 2– Changing values for positive predictive value (PPV) and number needed to treat (NNT) using different cut-off values for interferon-γ release assay (IGRA) positivity
IGRA cut-off IU·mL−1Total IGRA-positive contactsTotal contacts without PTContacts without PT onlyMissed TB cases
PPV %NNT
0.352542062.952.80
1.02061663.642.60
2.01591234.931.50
3.01351015.031.11
4.0121885.727.11
5.0111796.324.31
6.0104736.822.51
7.096667.620.31
8.089608.318.51
9.085588.617.81
>10.076549.316.61
  • Data are presented as n, unless otherwise stated. PT: preventive treatment.