Usefulness of the Combination of Tuberculin Skin Test and Interferon-Gamma Release Assay in Diagnosing Children with Tuberculosis

Usefulness of the Combination of Tuberculin Skin Test and Interferon-Gamma Release Assay in Diagnosing Children with Tuberculosis

HIROYUKI SHIMIZU^1,2 and MASAAKI MORI³

¹Children's Medical Center, Yokohama City University Medical Center, Yokohama, Kanagawa, Japan
²Department of Infection Prevention and Control, Yokohama City University Medical Center, Yokohama, Kanagawa, Japan
³Department of Lifetime Clinical Immunology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan

Japan is still designated as a medium incidence country, worldwide. Although the definitive diagnosis of tuberculosis is made by detecting pathogen from tissue specimens, collecting those from children is physically difficult. Therefore, we must frequently depend on the results of tuberculin skin test (TST) or interferon-gamma release assay (IGRA). However, the value of IGRA in diagnosing tuberculosis in infants remains unclear. We implemented TST and IGRA concurrently and examined the significance of combining these two tests by analyzing cases where conflicting results were evident from other tests. Subjects included 52 children (24 boys, 28 girls) age 15 years or younger (4.0 ± 3.4 years) who visited our hospital for close examination after medical checkup for tuberculosis contact tracing. The children underwent TST, T-SPOT^®.TB, chest plain radiography, and chest computed tomography with a view to tuberculosis diagnosis during a 26-months period from January 2013 to March 2015. T-SPOT results were positive in 9/52 cases (17.3%), and TST results were positive in 12/52 cases (23.1%). Conflicting results were observed in 7/52 cases (13.5%), and all cases were treated as latent tuberculosis infection or incident cases of tuberculosis. The value of T-SPOT in tuberculosis diagnosis in children is still being established. However, there are a number of cases where conflicting results for T-SPOT and TST are indicated. Thus, it is currently desirable to use T-SPOT and TST concomitantly for children at an early age, especially for children below the age of 5 years, as a diagnostic measure in complementing other techniques.

keywords —— Interferon-gamma release assay; latent tuberculosis infection; Mycobacterium tuberculosis; pediatric tuberculosis; tuberculin skin test

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Tohoku J. Exp. Med., 2017, 243, 205-210

Correspondence: Hiroyuki Shimizu, M.D. Ph.D., Department of Infection Prevention and Control, Yokohama City University Medical Center, 4-57 Urafune-cho, Minami-ku, Yokohama, Kanagawa 232-0024, Japan.

e-mail: hiroyuki@yokohama-cu.ac.jp

Masaaki Mori, M.D. Ph.D., Department of Lifetime Clinical Immunology, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan.

e-mail: mori.phv@tmd.ac.jp