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Pulm Med. 2012;2012:757152. doi: 10.1155/2012/757152. Epub 2012 Dec 17.

Levels of interferon-gamma increase after treatment for latent tuberculosis infection in a high-transmission setting.

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Advanced Laboratory of Public Health, Oswaldo Cruz Foundation, Gonçalo Moniz Research Center, Salvador, Bahia 40296 710, Brazil.



We investigated IFN-γ levels before and after a six month course of isoniazid among individuals with latent tuberculosis infection (LTBI) in a high-transmission setting.


A total of 26 household contacts of pulmonary tuberculosis patients who were positive for LTBI by tuberculin skin test completed six months of treatment and submitted a blood sample for a follow-up examination. The IFN-γ response to Mycobacterium tuberculosis-specific antigens was measured, and the results before and after the completion of LTBI treatment were compared.


Of the 26 study participants, 25 (96%) showed an IFN-γ level higher than their baseline level before treatment (P ≤ 0.001). Only one individual had a decreased IFN-γ level after treatment but remained positive for LTBI.


In a high-transmission setting, the IFN-γ level has increased after LTBI treatment. Further studies must be undertaken to understand if this elevation is transient.

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