Screening for tuberculosis infection among newly arrived asylum seekers: Comparison of QuantiFERON®TB Gold with tuberculin skin test
Winje, Brita Askeland; Oftung, Fredrik; Korsvold, Gro Ellen; Mannsåker, Turid; Jeppesen, Anette Skistad; Harstad, Ingunn; Heier, Berit Tafjord; Heldal, Einar
Abstract
Background: QuantiFERON®TB Gold (QFT) is a promising blood test for tuberculosis infection
but with few data so far from immigrant screening. The aim of this study was to compare results
of QFT and tuberculin skin test (TST) among newly arrived asylum seekers in Norway and to assess
the role of QFT in routine diagnostic screening for latent tuberculosis infection.
Methods: The 1000 asylum seekers (age ≥ 18 years) enrolled in the study were voluntarily
recruited from 2813 consecutive asylum seekers arriving at the national reception centre from
September 2005 to June 2006. Participation included a QFT test and a questionnaire in addition to
the mandatory TST and chest X-ray.
Results: Among 912 asylum seekers with valid test results, 29% (264) had a positive QFT test
whereas 50% (460) tested positive with TST (indurations ≥ 6 mm), indicating a high proportion of
latent infection within this group. Among the TST positive participants 50% were QFT negative,
whereas 7% of the TST negative participants were QFT positive. There was a significant association
between increase in size of TST result and the likelihood of being QFT positive. Agreement
between the tests was 71–79% depending on the chosen TST cut-off and it was higher for nonvaccinated
individuals.
Conclusion: By using QFT in routine screening, further follow-up could be avoided in 43% of the
asylum seekers who would have been referred if based only on a positive TST (≥ 6 mm). The
proportion of individuals referred will be the same whether QFT replaces TST or is used as a
supplement to confirm a positive TST, but the number tested will vary greatly. All three screening
approaches would identify the same proportion (88–89%) of asylum seekers with a positive QFT
and/or a TST ≥ 15 mm, but different groups will be missed.