Comparing the tuberculin skin test and T-SPOT.TB blood test in children

Interferon-γ-release assays (IGRAs) have been developed for the diagnosis of tuberculosis infection, but few data are available for children. There currently is no reference standard for the diagnosis of tuberculosis infection.

To compare the performance of 1 IGRA, the T-SPOT.TB assay with the tuberculin skin test (TST) in children with different epidemiologic risk factors for tuberculosis.

We conducted a prospective study of 210 patients referred to 3 pediatric tuberculosis clinics, including those with no risk factors for tuberculosis (low risk, n = 27), risk factors but no identifiable source case (intermediate risk, n = 78), contact with a known source case (high risk, n = 74), and active disease (n = 31). Children were tested with TST and T-SPOT.TB. Concordance analyses were performed, and assay outcomes were modeled by multivariate logistic regression.

For 13 children with culture-confirmed tuberculosis disease, sensitivity of TST and T-SPOT.TB was 77% and 92%, respectively, and concordance was 69%. For high-risk children, concordance was 94% for BCG-unimmunized children and 88% for BCG-immunized children. For intermediate-risk children, concordance was 74% for BCG-unimmunized children and 33% for BCG-immunized children. For low-risk children, concordance was 74% for BCG-unimmunized children and 20% for BCG-immunized children. Multivariate analysis revealed that contact with a source case was associated with T-SPOT.TB result, but age and BCG immunization were not.

T-SPOT.TB is comparable to the TST in the diagnosis of tuberculosis disease and identification of high-risk children with tuberculosis infection and is more specific than the TST in children who have received the BCG vaccine.