Interferon-γ release assays versus tuberculin skin test for targeting people for tuberculosis preventive treatment: an evidence-based review.

OBJECTIVES

To assess whether Interferon-γ release assays (IGRAs) reduce the number of people considered for tuberculosis (TB) preventive treatment without increasing subsequent active disease.

METHODS

Longitudinal studies with both tuberculin skin test (TST) and IGRAs were identified through a PubMed search. Reductions in diagnosis of TB infection and increases in incident TB in people considered not infected, using IGRAs either instead of TST or as a confirmatory test (two-step approach), were assessed.

RESULTS

In comparison with TST alone, the pooled reductions in diagnosis of TB infection obtained with IGRAs were 16.7% and 5.8% at 5 and 10 mm cut-offs respectively, and 24.5% and 12.4% at 5 and 10 mm respectively with the two-step approach. Compared with TST alone, incident TB among people considered not infected increased with the two-step approach (0.94% with T-SPOT(®).TB and 1.1% with QuantiFERON(®)-TB Gold In-Tube) in one of seven studies in high-income countries. In middle- and low-income countries, two of four studies presented increases (0.08 and 0.03 per 100 patient-years respectively) with the two-step approach.

CONCLUSIONS

In high-income countries, the use of IGRAs, either instead of TST or as confirmatory test reduces the number of people considered for preventive treatment, without a significant risk of subsequent active disease.