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Table 4 True- and false-positive results a when changing from QFT-IT to T-Spot in screening for LTBI

From: Implications of the impact of prevalence on test thresholds and outcomes: lessons from tuberculosis

Country LTBI prevalenceb Increase in true positivesa,c Increase in false positivesa,c Increase in false positives for every true positive gained
United States 4.70% 329 12,389 37.7
Mexico 28.82% 2,018 9,253 4.6
Brazil 38.74% 2,712 7,964 2.9
Thailand 46.74% 3,272 6,924 2.1
Ivory Coast 54.62% 3,823 5,900 1.5
  1. LTBI, latent tuberculosis infection; QFT-IT, QuantiFERON-TB Gold In-Tube; T-Spot, T-SPOT.TB.
  2. a Based on a hypothetical population of 100,000 tested individuals.
  3. bSource: World Health Organization Global TB Database[4].
  4. c Sensitivity estimates: QFT-IT 81%, T-Spot 88%; specificity estimates: QFT-IT 99%, T-Spot 86%.