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. 2014 Jan 14;9(1):e85612.
doi: 10.1371/journal.pone.0085612. eCollection 2014.

Tuberculosis contact investigation using interferon-gamma release assay with chest x-ray and computed tomography

Akira Fujikawa  1 , Tatsuya Fujii  2 , Satoshi Mimura  3 , Ryota Takahashi  4 , Masao Sakai  3 , Shinya Suzuki  5 , Yukishige Kyoto  6 , Yasuhide Uwabe  7 , Shinji Maeda  8 , Toru Mori  9
Affiliations

Tuberculosis contact investigation using interferon-gamma release assay with chest x-ray and computed tomography

Akira Fujikawa et al. PLoS One. .

Abstract

Between September 2009 and January 2010, 6 members of the Japanese Eastern Army, who had completed the same training program, were diagnosed with active tuberculosis (TB) on different occasions. The Ministry of Defense conducted a contact investigation of all members who had come into contact with the infected members. The purpose of this study was to verify the efficacy of the TB screening protocol used in this investigation. A total of 884 subjects underwent interferon-gamma release assay (IGRA) and chest X-ray. The 132 subjects who were IGRA positive or with X-ray findings suggestive of TB subsequently underwent chest computer tomography (CT). Chest CT was performed for 132 subjects. Based on CT findings, 24 (2.7%) subjects were classified into the active TB group, 107 (12.1%) into the latent tuberculosis infection (LTBI) group, and 753 (85.2%) into the non-TB group. The first 2 groups underwent anti-TB therapy, and all 3 groups were followed for 2 years after treatment. Although one subject in the active TB group experienced relapse during the follow-up period, no patient in the LTBI or non-TB groups developed TB. IGRA and chest X-ray, followed by chest CT for those IGRA positive or with suspicious X-ray findings, appears to be an effective means of TB contact screening and infection prevention.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Contact investigation protocol for tuberculosis.
The subjects were stratified into 3 groups according to the results of QFT-3G, chest X-ray, and chest CT.
Figure 2
Figure 2. CT findings of active TB.
A chest CT image of the left upper lobe of the lung in a 19-year-old subject demonstrated clustered non-calcified nodules associated with dilated peripheral airways (thin arrows) and a cavitation (arrow head) with dilated and thickened subsegmental bronchus (white arrow).
Figure 3
Figure 3. Bacteriologically positive cases of active tuberculosis diagnosed by the investigation protocol.
Ten of 24 subjects diagnosed with active TB in the protocol showed positive culture for M. tuberculosis. Of these 10 subjects, 3 were missed by chest X-ray.
Figure 4
Figure 4. Comparison of QFT-3G values at screening between the active TB group and latent (LTBI) group.
Comparison showed a statistically significantly higher value in the active TB group than in the LTBI group.
Figure 5
Figure 5. Comparison of QFT-3G values between the positive and negative culture groups at diagnosis of active TB.
Comparison showed no significant difference between the 2 groups.
Figure 6
Figure 6. Comparison of QFT-3G values at diagnosis and after treatment of active TB.
Comparison showed a statistically significant reduction of QFT-3G values after treatment.
Figure 7
Figure 7. Comparison of QFT-3G values at diagnosis and after treatment of latent TB.
Comparison showed a statistically significant reduction of the QFT-3G values after treatment.
See this image and copyright information in PMC

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