Table 3.
Numbers needed to treat to prevent one case of TB in people with a positive IGRA or TST test result in different risk-groups in low incidence countries
| Study | Country | Population | LTBI test | LTBI positive (%) | Number followed longitudinally | TB cases incident | Sensitivity % | Specificity % | PPV % | NPV % | NNT |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Zellweger et al [36] | Europe | contacts | QFT-G-IT | 1067 (27.4%) | 3425 | 20 | 85.0 | 74.0 | 1.9 | 99.9 | 37 |
| T-SPOT.TB | 299 (26.6%) | 1061 | 4 | 50 | 73.6 | 0.7 | 99.7 | 37 | |||
| Geis et al [47] | Germany | contacts | QFT-G-ITc | 306 (19.3%) | 254 | 6 | 100 | n.d. | 2.5 | n.d. | 34 |
| Sloot et al [48] | Netherlands | contacts | TST/QFT-G-IT | 739 (15.5%) | 4716 | 17 | 76.5 | 85.8 | 1.9 | 99.9 | 89 |
| Close contacts | TST/QFT-G-IT | 1622 | 10 | 90 | 79 | 2.6 | 99.9 | 30 | |||
| Kik et al [51] | Netherlands | Migrant contacts | TSTd | 339 | 339 | 8 | 87.5 | n.d. | 3.8 | n.d. | 26 |
| QFT-G-IT | 178 | 327 | 8 | 62.5 | n.d. | 2.8 | n.d. | 36 | |||
| T-SPOT.TB | 181 | 299 | 8 | 75 | n.d. | 3.3 | n.d. | 30 | |||
| Hermansen et al [49] | Denmark | Mixeda | QFT-G-IT | 1703 (10.7%) | 15980 | 40 | 50 | 88.7 | 1.32 | 99.9 | 68e |
| Sester et al [8] | Europe | Immuno-compromisedb | TST | 212 (14.1%) | 1404 | 6 | 50 | 86.2 | 1.5 | 99.8 | 50 |
| QFT-G-IT | 239 (15.6%) | 1342 | 4 | 50 | 84.1 | 0.9 | 99.8 | 80 | |||
| T-SPOT.TB | 266 (17.7%) | 1310 | 6 | 50 | 81.3 | 1.3 | 99.7 | 64 | |||
| HIV only | TST | 55 (8.7%) | 626 | 6 | 50 | 93.7 | 7.1 | 99.5 | 14 | ||
| QFT-G-IT | 83 (13.1%) | 621 | 4 | 50 | 92.1 | 3.9 | 99.6 | 26 | |||
| T-SPOT.TB | 101 (15.9%) | 561 | 6 | 50 | 89 | 4.7 | 99.4 | 21 | |||
| HIV positive HIV load | TST | 24 (8.1%) | 291 | 6 | 50 | 92.6 | 12.5 | 98.9 | 8 | ||
| QFT-G-IT | 25 (8.4%) | 289 | 4 | 50 | 91.9 | 8 | 99.2 | 13 | |||
| T-SPOT.TB | 31 (10.4%) | 255 | 6 | 50 | 88.8 | 9.7 | 98.7 | 10 | |||
| Schablon et al [50] | Germany | HCW | QFT-G-IT | 317 (8.3%) | 3823 | 0 | 0 | 91.7 | 0 | 100 | n.a.f |
| Slater et al [43] | USA | HCW | QFT-G-IT | 853 (9.3%) | 9153 | 0 | 0 | 90.7 | 0 | 100 | n.a.f |
| Dorman et al [42] | USA | HCW | TST | 125 (5.2%) | 2418 | 0 | 0 | 94.8 | 0 | 100 | n.a.f |
| QFT-G-IT | 118 (4.9%) | 2418 | 0 | 0 | 95.1 | 0 | 100 | n.a.f | |||
| T-SPOT.TB | 144 (6.0%) | 2418 | 0 | 0 | 94 | 0 | 100 | n.a.f |
aindividuals included contacts, patients prior to TNF antagonist treatment, and TB suspects;
bindividuals included patients with chronic renal failure, patients prior to TNF antagonist treatment, solid organ- and stem cell transplant recipients, and HIV infected patients; PPV, positive predictive value; NPV, negative predictive value; NNT, number needed to treat to prevent a case of TB; LTBI, latent infection with M. tuberculosis; TST, tuberculin skin test; QFT-G-IT, QuantiFERON gold in tube; HCW, health-care workers; PPV and NPV were calculated from all individuals with and without preventive chemotherapy;
conly IGRA-positive individuals were included and followed longitudinally;
donly TST positive individuals were included and followed longitudinally;
eassumption no case of TB in IPT treated individuals, 35% INH coverage among test positives;
fno cases of active TB.