II. Diagnostic Tests for Latent TB Infection (LTBI)

Last Updated April 2026

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There is no "gold standard" test for latent TB infection (LTBI). Two types of diagnostic tests to detect LTBI are commercially available. These include the tuberculin skin test (TST) which has been available for > 100 years and a newer generation of diagnostic tests, the interferon-γ release assays (IGRAs), which are T-cell-based in - vitro blood tests. Two IGRAs are approved for use by the U.S. FDA. Neither the TST nor IGRA tests can distinguish LTBI from active TB disease.

List of sub chapters

• Tuberculin Skin Test (TST)
• Criteria for a Positive Tuberculin Test, by Risk Group
• Two-Step Testing and the Booster Reaction
• Anergy Testing
• Interferon-γ Release Assays (IGRAs)
• Targeted Testing and Diagnostic Tests for LTBI
• Medical Evaluation After Testing for LTBI
• Reporting of Pediatric Positive Tests for LTBI

List of charts

• Table 1. Interpretation Criteria for the QuantiFERON-TB Gold Plus Test (QFT-Plus)
• Table 2. Interpretation Criteria for the T-SPOT.TB Test (T-Spot)
• Table 3. High Prevalence and High Risk Groups