Table 3 Screening recommendations in low-incidence countries based on TB incidence, positive predictive value of IGRAs and TST for progression to active TB disease, and number needed to screen
Country or Region | Risk Sub-group Studied | Screening Tool | 2015 National TB Incidence (reported cases/million population/year) [58] | PPV a for Progression to Active Disease | NNT b or NNS c | Screening Tool Recommendations | Screening Strategy Recommendations |
|---|---|---|---|---|---|---|---|
Canada | Indigenous individuals [24] d | TST | 45.55 | NR | NNS: 5.3 | Use of the TST in the paediatric population, although IGRAs may be preferable in areas where BCG vaccination persists | Location-based screening in Indigenous communities with > 5 TB cases in the past 5 years [24] |
Individuals in long-term care facilitiesd [59] | TST | Â | NR | 1410 | |||
Australia | Immigrant/refugee children or child contacts of TB cases | TST & IGRAs | 52.25 | NR | NR | Although prior studies indicate potentially poorer sensitivity of IGRAs compared to the TST, [38, 43]the basis of this conclusion in the absence of a gold standard diagnostic tool is unclear, and a more recent study suggests poorer sensitivity of the TST compared to IGRAs for the detection of LTBI, based on a prospective follow-up of study subjects. [44] | Â |
Italy | Immigrant children and child contacts of TB cases | TST & IGRAs | 62.82 | NR | NR | Use of IGRAs recommended in BCG-vaccinated paediatric populations [56] | Â |
Spain | Immigrant children [47] | QFT-GIT & TST | 91.12 | NR | NR | Use of IGRAs is preferential in low-incidence settings to prevent unnecessary prophylactic treatment | Risk-based screening: contacts of TB cases and undocumented immigrant children [46, 47] |
Contacts of TB cases [46] | QFT-GIT & TST | Â | NR | NR | |||
United Kingdom [33] | Immigrant children from low-incidence countries (< 150/100,000) | NR | 96.00 | NR | NNS: 5291 | IGRAs are more cost-effective in low-incidence countries [37] | Risk-factor-based screening: immigrants from high-incidence countries [33,34,35] |
Immigrant children from high-incidence countries (> 500/100,000) | NR |  | NR | 88 | |||
United States | Immigrants d [60] | TST | 29.66 | NR | NNS: 150 | IGRAs are a better predictor of progression to active disease in paediatric populations [40, 41] | Risk-factor-based screening: immigration status, malnutrition [31, 32, 36] |
Europe d [54] | Immune-compromised individuals [61] | TST QFT-GIT T-SPOT.TB | NA | 1.5 0.9 1.3 | NNT: 50 80 60 | Â | Targeted screening of close contacts [54] |
Contacts of TB cases [62] | QFT-GIT T-SPOT.TB | NA | 1.9 0.7 | 37 37 |