Discordant results between all three tests were common with
percentage agreement ranging from 46.1% to 88.9% (table 3).
Using different cut-off values for the TST did not improve the
yield or test agreement significantly (proportion positive: 73.0%,
69.2% and 65.4% for TST cut-off values of 5, 10 and 15 mm,
respectively, in all subjects).
Table 4 shows the relation between exposure to M tuberculosis
and IGRA results. Participants with a highMtuberculosis contact
score were at least seven times more likely to be T-SPOT.TB
positive than those with a low score (odds ratio (OR) 62.42,
95% CI 7.67 to 508.69) regardless of age, and at least three times
more likely to be QTF positive (OR 9.60, 95% CI 3.02 to 30.54).
This relationship was confounded by age. The TST was not
significantly associated with M tuberculosis exposure in unadjusted
or adjusted regression models. Using a higher M
tuberculosis exposure score cut-off value of 8 decreased the
association between M tuberculosis exposure and measures of
infection (data not shown).