Abstract

MACHADO-VILLARROEL, Limberth et al. Determination of interferon-gamma in tuberculosis: basic principles and utility. Neumol. cir. torax [online]. 2015, vol.74, n.3, pp.197-206. ISSN 0028-3746.

Tuberculosis is a globally distributed communicable disease with high rates of morbimortality. It is fundamental to establish an opportune diagnosis and treatment of latent tuberculosis infection, reducing the risk of progression to active tuberculosis. Tuberculin skin test is the standard screening method for latent tuberculosis infection, however, it presents limitations in its performance, low sensitivity and specificity, mostly in immunocompromised individuals and/or previously vaccinated with Bacillus Calmette-Guérin. IGRA (Interferon-Gamma Release Assay) test was designed to improve latent tuberculosis infection diagnosis and to increase sensitivity and specificity by means of quantifying interferon-gamma produced by sensitized T lymphocytes in response to contact with specific Mycobacterium tuberculosis antigens. IGRA test is still incapable to discriminate neither previous from current Mycobacterium tuberculosis infection, nor differentiate between latent tuberculosis infection and active tuberculosis. Two commercially available IGRA tests exist: QuantiFERON^®-TB Gold In-Tube and T-SPOT^®.TB. Performance is superior in immunocompetent individuals > 5 years old. Clinical efficacy is affected in immunocompromised individuals owing to a reduced and fluctuant interferon-gamma synthesis in such group of patients. Factors such as immunosuppression contribute to obtain indeterminate results, which must be taken into account when interpreting the test.

Keywords : Interferon-gamma release assays; interferon-gamma; latent tuberculosis; T-lymphocytes.

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