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Correspondence |

Questions in the Role of Chest CT Scanning in TB Outbreak Investigation FREE TO VIEW

Sourin Bhuniya, MD, FCCP; Pampa De, DNB
Author and Funding Information

From the Department of Chest Medicine (Dr Bhuniya), R. G. Kar Medical College and Hospital; and the Department of Physical Medicine and Rehabilitation (Dr De), National Institute for the Orthopaedically Handicapped.

Correspondence to: Sourin Bhuniya, MD, FCCP, 66CC/5, Anupama Housing Complex, Phase-2, VIP Rd, Kolkata-700052, India; e-mail: sbhuniya@hotmail.com


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).


© 2010 American College of Chest Physicians


Chest. 2010;138(6):1522-1523. doi:10.1378/chest.10-1249
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To the Editor:

The study by Won Lee and colleagues1 from South Korea in the recent issue of CHEST (May 2010) has generated a number of important issues and questions that need to be highlighted. The authors have diagnosed active pulmonary TB (PTB) in about 21% of patients, and it is really hard to believe this unusually high rate of active disease, especially when all the patients are young soldiers who are immunocompetent and healthy.

It is quite surprising that none of the 18 cases of active PTB that were diagnosed using high-resolution CT (HRCT) scans showed positive acid-fast staining of the sputum specimens. Among the nine cases of active PTB diagnosed on the basis of CT scanning alone, two patients had neither any symptoms nor a positive sputum test result for acid-fast bacilli culture. Did these soldiers really have active PTB? How often do we see patients with active PTB who have no symptoms? Was administering a full course of antitubercular treatment for 6 months to these patients justified?

The authors have claimed symptomatic or radiographic improvement in all cases of active PTB. Therefore, in those nine patients with normal chest radiographs and active PTB, follow-up HRCT scans of the thorax must have been done to assess radiologic improvement. How do we view this very high dose of radiation exposure in these young soldiers? It is well known that radiation generates highly reactive free radicals and is carcinogenic, teratogenic, and mutagenic. It has been associated with cancers of the thyroid, bone, lung, breast, and leukocytes.2 Like lead and asbestos, radiation has no safe threshold. Therefore, performing HRCT scans of the thorax in only those patients who have symptoms suggestive of active PTB seems to be a more pragmatic approach.

The authors have relied heavily on the results of interferon-γ (INF-γ) release assay in a few patients for the diagnosis of active PTB, even in the absence of clinical symptoms. It is well known that higher production of INF-γ correlates to some extent with the activity of Mycobacterium tuberculosis infection, but its low sensitivity and specificity for distinguishing active vs latent TB has been demonstrated by various studies worldwide, and therefore it is not recommended as a diagnostic tool for active TB.3-5 We ought to be more judicious with the use of antitubercular therapy, especially when the threat of multidrug resistance and extensively drug-resistant TB is hovering over us.

Lee SW, Jang YS, Park CM, et al. The role of chest CT scanning in TB outbreak investigation. Chest. 2010;1375:1057-1064. [CrossRef] [PubMed]
 
Jacobson JA.Beers M, Porter R, Jones T, et al. Radiation injury. The Merck Manual of Diagnosis and Therapy. 2006;18th ed Whitehouse Station, NJ Merck Research Laboratories:2601:2609
 
Browatzki A, Meyer CN. Interferon-gamma release assay on suspicion of active tuberculosis? [in Danish]. Ugeskr Laeger. 2009;17137:2631-2635. [PubMed]
 
Dewan PK, Grinsdale J, Kawamura LM. Low sensitivity of a whole-blood interferon-gamma release assay for detection of active tuberculosis. Clin Infect Dis. 2007;441:69-73. [CrossRef] [PubMed]
 
Janssens JP, Roux-Lombard P, Perneger T, Metzger M, Vivien R, Rochat T. Quantitative scoring of an interferon-γ assay for differentiating active from latent tuberculosis. Eur Respir J. 2007;304:722-728. [CrossRef] [PubMed]
 

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References

Lee SW, Jang YS, Park CM, et al. The role of chest CT scanning in TB outbreak investigation. Chest. 2010;1375:1057-1064. [CrossRef] [PubMed]
 
Jacobson JA.Beers M, Porter R, Jones T, et al. Radiation injury. The Merck Manual of Diagnosis and Therapy. 2006;18th ed Whitehouse Station, NJ Merck Research Laboratories:2601:2609
 
Browatzki A, Meyer CN. Interferon-gamma release assay on suspicion of active tuberculosis? [in Danish]. Ugeskr Laeger. 2009;17137:2631-2635. [PubMed]
 
Dewan PK, Grinsdale J, Kawamura LM. Low sensitivity of a whole-blood interferon-gamma release assay for detection of active tuberculosis. Clin Infect Dis. 2007;441:69-73. [CrossRef] [PubMed]
 
Janssens JP, Roux-Lombard P, Perneger T, Metzger M, Vivien R, Rochat T. Quantitative scoring of an interferon-γ assay for differentiating active from latent tuberculosis. Eur Respir J. 2007;304:722-728. [CrossRef] [PubMed]
 
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