Latent TB Infection (LTBI) — The Move Beyond TST
Identifying patients with latent TB is essential for preventing future cases. In 2026, traditional skin tests are being replaced by high-specificity blood and antigen tests.
Interferon-Gamma Release Assays (IGRAs): Tests like QuantiFERON-TB Gold Plus and T-SPOT.TB measure the immune system's response to specific TB antigens. Unlike older tests, IGRAs are not affected by previous BCG vaccinations.
Antigen-Based Skin Tests (e.g., Cy-Tb): A new class of skin tests has emerged that combines the simplicity of the old Tuberculin Skin Test (TST) with the high specificity of an IGRA. These tests (like the Serum Institute of India’s Cy-Tb) use specific antigens (ESAT-6/CFP-10) to avoid false positives from the BCG vaccine.
