Interferon-release assays (IGRAs) represent advances in tuberculosis immunology and evolutionary biology. IGRAs were designed to replace tuberculin skin test (TST) for the diagnosis of latent tuberculosis infection because of their logistical advantages and enhanced specificity over TST. Although IGRAs and TST have been useful in epidemiologic studies, they lack the sensitivity and reproducibility normally expected from diagnostic tests in clinical practice. In this review, we present an overview of the current recommendations and knowledge in the field and discuss practical approaches in areas of uncertainty related to discordant IGRA results.