Interferon Gamma Release Assay for Identifying Latent Tuberculosis Infection in People With Bacillus Calmette-Guérin Vaccination

There are 2 accepted tests for the identification of latent tuberculosis infection (LTBI), the tuberculin skin test (TST) and the interferon gamma release assay (IGRA). TST involves an intradermal injection of a purified protein derivative into the lower part of the arm and waiting to see whether the patient has a reaction to the injection; whereas, IGRA is a blood test that measures the person’s immune response to TB proteins. There are differences with regard to the cost, ease of use, skill, and laboratory equipment required for these 2 tests. There may be differences in the accuracy of these tests in specific populations, such as those with previous Bacillus Calmette-Guérin (BCG) vaccination. In August 2020, CADTH searched the literature for evidence on the clinical utility, the costeffectiveness, and evidence-based guidelines regarding the use of the IGRA for identifying LTBI in people with previous BCG vaccination. That report identified 1 non-randomized study and 1 evidence-based guideline that were potentially relevant, but no economic evaluations. The purpose of the current report is to review the full texts of these publications, and to summarize and critically appraise the eligible publications. This report is a component of a larger CADTH Condition Level Review on Tuberculosis. A condition level review is an assessment that incorporates all aspects of a condition, including prevention, detection, treatment, and management. For more information on CADTH’s Condition Level Review of Tuberculosis, please visit the project page (https://www.cadth.ca/tuberculosis).