Contribution of the interferon-gamma release assay to tuberculosis diagnosis in children and adolescents

Setting As conclusive data on the performance of interferon-gamma release assays (IGRAs) in paediatric TB are lacking, many guidelines do not recommend their use for TB diagnosis in this population in Brazil. Objective To evaluate the performance of an IGRA by investigating its concordance with the tuberculin skin test (TST) and the role of IGRAs in clinical management and treatment outcomes in children with TB. Design A historic cohort study was used to evaluate the performance of T-SPOT®.TB (ELISpot) and other tests, such as the TST, in paediatric patients with or without immunodeficiency who were under investigation for latent tuberculous infection (LTBI) or active tuberculosis (TB). Results Of 86 paediatric patients evaluated, 41 (48%) were immunocompetent and 45 (52%) immunocompromised. All patients underwent T-SPOT.TB, while 63 underwent both ELISpot and TST; test results were concordant in 50 patients (79.4%): 22/31 (71%) in immunocompetent (κ = 0.418, P = 0.02) and 28/32 (87.5%) in immunocompromised patients (κ = 0.526, P = 0.003). TB was diagnosed on the basis of the ELISpot result in 21% (18/86) cases; the contribution of the ELISpot assay was greater in immunocompetent patients than in those who were immunocompromised (13/41, 31.7% vs. 5/45, 11.1%, χ2 P = 0.038). Conclusion ELISpot and TST results were moderately concordant in both groups of patients. ELISpot contribution was higher among immunocompetent patients than among immunocompromised patients.