IFNG and tuberculosis: At present, the population having preventive therapy for LTBI in China is mainly students who are in close contact with confirmed active tuberculosis patients in a tuberculosis outbreak in a school and who have a tuberculin skin test (TST) induration diameter ≥15 mm or are accompanied by vesicular lymphangitis or strongly positive TST results or a positive interferon-gamma release assay (IGRA) test (National Health Commission, 2020).