A tuberculosis contact investigation involving a large number of contacts tested with interferon-gamma release assay at a nursing school: Kanagawa, Japan, 2012

Authors

  • Masako Tasaka Kanagawa Prefectural Institute of Public Health, Kanagawa, Japan
  • Tamae Shimamura Research Institute of Tuberculosis, Tokyo, Japan
  • Mami Iwata Naka Welfare and Health Office, Yokohama, Japan
  • Takahiro Toyozawa Yokohama City Health Department, Yokohama, Japan
  • Masaki Ota Research Institute of Tuberculosis, Tokyo, Japan https://orcid.org/0000-0002-3539-4535

DOI:

https://doi.org/10.5365/wpsar.2018.9.1.001

Abstract

Objectives: In May 2012, a teacher of a nursing school with nearly 300 staff members and students in Japan was diagnosed with sputum smear-positive pulmonary tuberculosis (TB), leading to a large contact investigation involving nearly 300 contacts. Herein we describe the contacts’ closeness to the index TB patient and the positivity of interferon-gamma release assay (IGRA).  

Methods: TB was diagnosed when a person had samples that tested bacteriologically positive for TB, or  was determined to have TB by a physician. A latent TB infection (LTBI) case was defined as one in which a person tested positive in IGRA.

Results: A total of 288 persons were screened with IGRA; however, two were excluded because of histories of TB and LTBI treatment; thus 286 were analyzed. Eleven persons (3.8%, 95% confidence interval [95%CI]: 1.9-6.8) tested positive for IGRA. Of the 11, a third year student was found to have pulmonary TB disease by chest X-ray. The positivity in IGRA among close contact staff members (4 of 21, 19%, 95%CI: 5.4-42%) with a statistically significant relative risk of 17 (95%CI: 2.0-140) was high compared with that of the third year students (1 of 88, 1.1% [95%CI: 0.028-6.2]). The Cochran-Armitage test revealed a statistically significant trend in the risk of TB infection among the staff and students (close contact staff> 2nd year> 1st year> 3rd year students, p<0.0025).

Discussion: The authors thus recommend that teachers should undergo health examinations, including regular chest X-ray examinations.


Author Biographies

Masako Tasaka, Kanagawa Prefectural Institute of Public Health, Kanagawa, Japan

Research Scientist, Epidemiology Department

Mami Iwata, Naka Welfare and Health Office, Yokohama, Japan

Head, Naka Welfare and Health Office

Takahiro Toyozawa, Yokohama City Health Department, Yokohama, Japan

Director, Yokohama City Health Department

Masaki Ota, Research Institute of Tuberculosis, Tokyo, Japan

Head, Division of Technical Support for National Tuberculosis Programmes.

References

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Published

06-08-2018

How to Cite

1.
Tasaka M, Shimamura T, Iwata M, Toyozawa T, Ota M. A tuberculosis contact investigation involving a large number of contacts tested with interferon-gamma release assay at a nursing school: Kanagawa, Japan, 2012. Western Pac Surveill Response J [Internet]. 2018 Aug. 6 [cited 2026 Mar. 21];9(3). Available from: https://ojs.wpro.who.int/ojs/index.php/wpsar/article/view/584

Issue

Vol. 9 No. 3 (2018): July – September

Section

Field Investigation Report

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