Performance of the Tuberculin Skin Test and Interferon-γ Release Assays: An Update on the Accuracy, Cutoff Stratification, and New Potential Immune-based Approaches

An association between biologic agents and reactivation of active disease from latent tuberculosis infection (LTBI) has been established. Screening for LTBI is, therefore, now recommended for candidates for biologic drugs. The tuberculin skin test (TST) and interferon-γ release assays (IGRA) are the available commercial tests for detecting LTBI. We discuss their accuracy in immune-competent subjects and patients with autoimmune diseases, as well as potential new approaches to immune diagnosis. IGRA seem to be more accurate than TST in bacillus Calmette-Guerin vaccinated subjects and patients with autoimmune diseases. However, longitudinal studies are needed to estimate the risk of progression to TB after IGRA-based and/or TST-based diagnosis of LTBI in these vulnerable patients. New tests are needed to identify those patients with LTBI who will develop active TB and need prophylaxis.