Interferon-gamma release assays for diagnosis of latent tuberculosis infection: evidence in immune-mediated inflammatory disorders

Abstract

To provide a narrative synthesis of evidence on interferon-gamma release assays (IGRAs) for the diagnosis of latent tuberculosis infection (LTBI) in individuals with immune-mediated inflammatory disorders (IMIDs). Only a few studies have evaluated IGRAs in IMIDs, and most were small and varied considerably with respect to the use of immunosuppressive medications and types of IMIDs. Current evidence does not clearly suggest that IGRAs are better than tuberculin skin test (TST) in identifying individuals with IMID who could benefit from LTBI treatment. To date, no studies have been done on the predictive value of IGRAs in IMID patients. Important questions remain unanswered as to the impact of immunosuppressive medications and the impact of type of IMID on IGRA performance. Despite the lack of clear evidence, there is an increasing tendency for guidelines to prefer IGRA over TST in IMIDs or to recommend both TST and IGRA to enhance sensitivity. We believe the use of either test is acceptable for LTBI screening. Clinicians could consider starting with IGRAs in individuals with a history of Bacille Calmette-Guérin (BCG) vaccination after infancy or with repeated BCG vaccinations. When the index of suspicion for LTBI is high, both IGRA and TST could be performed, especially prior to initiating TNF-α inhibitor therapy. Regardless of the test used, it is important to remember that in the face of immune-suppression, both IGRA and TST can be falsely negative and are thus only diagnostic aids - they will need to be interpreted with other clinical and risk factor data.