Performance of Tuberculin Skin Test Measured against Interferon Gamma Release Assay as Reference Standard in Children.

Eisenhut M(1), Fidler K(2).
Objectives. International guidelines differ in the threshold of tuberculin skin test (TST) induration regarded as indicating Mycobacterium (M.) tuberculosis infection. Interferon gamma release assay (IGRA) results were used as reference to assess performance of TST induration thresholds for detection of M. tuberculosis infection in children.
Design. Systematic review which included studies containing data on TST, IGRA, and Bacillus Calmette-Guérin (BCG) status in children. Data bases searched were PubMed, EMBASE, and the Cochrane library. Specificities and sensitivities were calculated for TST thresholds 5, 10, and 15 mm and correlated with age and geographical latitude.
Results. Eleven studies with 2796 children were included. For BCG immunised children diameters of 5, 10, and 15 mm had median sensitivities of 87, 70, and 75% and specificities of 67, 93, and 90%, respectively. In non-BCG immunised children median sensitivities were 94, 95, and 83% and specificities 91, 95, and 97%. At the 10 mm threshold age correlated negatively with sensitivity of TST (r = -0.65, P = 0.04) and latitude correlated positively (r = 0.71, P = 0.02).

Conclusions. For the 10 mm threshold the sensitivity of the TST is lower in BCG immunised children. Younger  age and higher geographical latitude were associated with higher sensitivity of the TST.