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Curr Opin Pulm Med. 2009 Jul;15(4):358-65. doi: 10.1097/MCP.0b013e32832bcc4e.

Interferon-gamma release assays for the diagnosis of TB pleural effusions: hype or real hope?

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University of Bristol and North Bristol Lung Centre, Southmead Hospital, Bristol, UK.



T-cell interferon-gamma release assay (IGRA) use in tuberculosis (TB) contact screening and latent TB diagnosis is established and supported by American and European guidelines. However, questions remain regarding their clinical utility beyond conventional tests in the investigation of suspected active TB. We review the evidence base for IGRAs in the diagnosis or exclusion of pleural TB.


The specificity of IGRAs for diagnosis of active TB disease is limited by an inability to distinguish latent disease. The test's sensitivity when applied to the blood of patients with active TB is diminished by compartmentalizing of sensitized T cells at the disease site. To circumnavigate these problems, recent studies explore the value of applying IGRAs to pleural fluid. Results have varied between patient populations, but the strategy does not appear to completely eliminate false-positive results.


Accurate biomarkers of pleural TB are useful, particularly for their negative predictive value. IGRAs are technically more complicated and expensive than established biomarkers, and their diagnostic performance for active pleural TB is highly variable between studies and settings. Currently, there is inadequate evidence to support the use of IGRAs in the diagnosis or exclusion of active pleural TB, particularly in centres where adenosine deaminase and interferon-gamma assays are available.

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