Children had a higher mean M tuberculosis contact score than
adults, reflecting the importance of proximity of contact and
the duration of exposure to M tuberculosis experienced by young
children. In the majority of cases the index case was the child’s
parent or primary caregiver, consistent with previous findings.26
A key consideration for the interpretation of our findings is that
the majority of children had recent and significant documented
household exposure, whereas many adults had less reported
household exposure although they may have had previous or
remote M tuberculosis exposure. Adults had a higher probability
of being TST positive (78%) but a lower probability of being
IGRA positive (66% for T-SPOT.TB vs 39.6% for QTF),
suggesting higher IGRA specificity but lower sensitivity in the
presence of recent exposure.