Comparison of Results between Tuberculin Skin Test and QuantiFERON(R)-TB In-Tube Assay for Diagnosis of Latent Tuberculosis Infection in Children and Adolescents / 소아감염

ABSTRACT

PURPOSE: Recently, two tests are commercially available for the identification of latent tuberculosis infection (LTBI): tuberculin skin test (TST) and interferon-gamma release assay (IGRA). Due to its false positiveness, TST tends to be preferred by IGRA until now. In our study, we simultaneously performed both TST and QuantiFERON(R)-TB Gold In-Tube (QFT-GIT) and compared their results. METHODS: TST and QFT-GIT were done for the diagnosis of LTBI among children who visited pediatric out-patient clinic at St. Vincent's Hospital, The Catholic University of Korea from February of 2007 to May of 2008. The study group was stratified into two groups in terms of whether there was intrafamilial contact or not. RESULTS: Out of total 35 children, 29 were tuberculosis (TB)-exposed cases and the remainders were diagnosed as clinical pulmonary TB. Among these 29 children, TST was positive 38.9% (7/18) for the intrafamilial and 45.5% (5/11) for the non-intrafamilial, and at the same time, the result for QFT-GIT was positive 5.6% (1/18) and 9.1% (1/11), respectively which implies that TST was more sensitive than QFT-GIT. Among 29 TB-exposed cases, 26 initially went through TST and QFT-GIT together on their first visit to out-patient clinic, and 15 continued the follow-up tests. Out of total 41 cases collected, the agreement (known as kappa value) was 0.063 which was relatively low. Including 6 cases with pulmonary TB who were all positive for TST and only 5 being positive for QFT-GIT, the final kappa value was 0.334. CONCLUSION: In our study, the agreement for TST and QFT-GIT was low, and the majorities were almost the cases of positive TST. In current situation with lacking a gold standard test and limited data on children to adolescents, this result is quite alarming that the recent trend tends to replace TST by QFT-GIT when diagnosing LTBI.