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Correspondence |

The Journey From Latent to Active TBThe Journey From Latent to Active TB: No Roadmaps as Yet FREE TO VIEW

Alkesh K. Khurana, MD, DNB, FCCP; Ujjawal Khurana, MD, DNB
Author and Funding Information

From the Department of Pulmonary and Critical Care Medicine (Dr A. K. Khurana), Max Super Speciality Hospital; and the Department of Pathology (Dr U. Khurana), Grecian Super Speciality Hospital.

Correspondence to: Alkesh K. Khurana, MD, DNB, FCCP, Max Super Speciality Hospital, Pulmonary and Critical Care Medicine, Phase VI, Mohali, Punjab, India 160055; e-mail: lungcancer@rediffmail.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. See online for more details.


Chest. 2012;142(3):811. doi:10.1378/chest.12-1167
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To the Editor:

We read with great interest the article by Diel et al1 in CHEST (July 2012) discussing the positive predictive value of interferon-γ release assays (IGRAs). We appreciate their work, but we feel that a couple of issues need to be addressed.

First, the duration of treatment of previously untreated patients was kept as 2 years only. Although the risk of progression from latent TB infection (LTBI) to active TB is greatest in the first 2 years,2 in Southeast Asia, where TB burden is very high, the duration of follow-up is apparently much less. In countries like India, where the prevalence of LTBI (hence, positive IGRA or tuberculin skin test results) is very high, a follow-up of only 2 years for progression to active TB does not seem justified. This short follow-up period is probably sufficient for countries with a low TB burden. As a huge proportion of the population on the Southeast Asian subcontinent acquires TB infection in childhood only,3 it remains doubtful whether these tests can be used as a surrogate marker to predict the progression of TB infection.

Second, the utility of IGRAs in health-care workers remains dubious. The possibility of having a latent TB infection in this group is high for obvious reasons. Park et al4 found inconsistent IGRA results in more than one-half of the health-care professionals inducted in the study. Also, the concept of mass treatment based on positive LTBI results is apparently inappropriate in high-burden countries, as it would just lead to higher incidence of drug-resistant TB. Therefore, we believe that the results of this study should be seen from different perspectives, not only in context of the burden of the disease, but also in the context of the study participants’ professions.

Diel R, Loddenkemper R, Nienhaus A. Predictive value of interferon-γ release assays and tuberculin skin testing for progression from latent TB infection to disease state: a meta-analysis. Chest. 2012;142(1):63-75. [PubMed] [CrossRef]
 
Diel R, Goletti D, Ferrara G, et al. Interferon-γ release assays for the diagnosis of latentMycobacterium tuberculosisinfection: a systematic review and meta-analysis. Eur Respir J. 2011;37(1):88-99. [PubMed] [CrossRef]
 
World Health Organization 2011/2012 Tuberculosis Global Facts. 2011 Geneva, Switzerland World Health Organization.
 
Park JS, Lee JS, Kim MY, et al. Monthly follow-ups of interferon-γ release assays among healthcare workers in contact with TB patients [published online ahead of print May 3, 2012]. Chest. doi:10.1378/chest.11-3299.
 

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References

Diel R, Loddenkemper R, Nienhaus A. Predictive value of interferon-γ release assays and tuberculin skin testing for progression from latent TB infection to disease state: a meta-analysis. Chest. 2012;142(1):63-75. [PubMed] [CrossRef]
 
Diel R, Goletti D, Ferrara G, et al. Interferon-γ release assays for the diagnosis of latentMycobacterium tuberculosisinfection: a systematic review and meta-analysis. Eur Respir J. 2011;37(1):88-99. [PubMed] [CrossRef]
 
World Health Organization 2011/2012 Tuberculosis Global Facts. 2011 Geneva, Switzerland World Health Organization.
 
Park JS, Lee JS, Kim MY, et al. Monthly follow-ups of interferon-γ release assays among healthcare workers in contact with TB patients [published online ahead of print May 3, 2012]. Chest. doi:10.1378/chest.11-3299.
 
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