Tuberculosis screening programme for undocumented immigrant teenagers using the QuantiFERON®-TB Gold In-Tube test

Abstract

Background and objectiveThe aim of this study was to determine the prevalence of tuberculosis infection in undocumented immigrant teenagers using a tuberculin skin test (TST) for initial screening and QuantiFERON®-TB Gold In-Tube (QFT-GIT) as a confirmatory test. Patient and methodFrom 2007 to 2012, under 19-year-old immigrant teenagers from 2 accommodation centres of the Basque Country (Spain) were included in the study. The TST was done in all of them and the QFT-GIT was done in selected patients with a TST≥5mm. ResultsEight hundred and forty-five immigrants were included, most of them from Africa (99.5%). Fifty-one percent of immigrants with TST≥5mm has a positive QFT-GIT. We found 2 cases of active tuberculosis (2/845: 0.24%). The concordance between TST (≥10mm) and QFT-GIT was 63%, with 57% of positive concordance cases and 96% of negative concordances. There were 246 cases with TST≥10mm (29%), with significant differences between Magrebis (21.5%) and Subsaharians (67%) (p<0.001). Vaccination with Calmette-Guéin bacille was an independent predictor for having a TST≥10mm (OR: 2.11; p<0.001) and for the discordance TST+/QFT-GIT−, both for a TST≥5 and a TST≥10mm (OR 2.16, 95% confidence interval [95% CI] 1.46–3.20, and OR 1.91 95% CI 1.23–2.97, respectively). The positive value of QFT-GIT increased significantly as the TST increased, with a positive association in all the cut-off points analysed: 10–14mm (OR 7.95, 95% CI 1.79–35.33), 15–19mm (OR 35, 95% CI 7.93–154.52) and ≥20mm (OR 91.3, 95% CI 18.20–458.11). ConclusionDue to the high prevalence of latent tuberculosis infection in Subsaharian immigrants, we recommend implementing screening programmes in this population. Using QFT-GIT, the number of candidates for chemoprophylaxis was reduced to 43% compared with TST alone (≥10mm).