Comparison of Interferon-Gamma Release Assay and Tuberculin Skin Test in Screening for Latent Tuberculous Infection Among Students from High-Burden Areas: A Prospective Head-to-Head Study in Qingdao, China

BACKGROUND: Identifying latent tuberculosis infection (LTBI) is critical for pediatric TB control in China, especially among students from high-burden areas. With no gold-standard test, we compared the tuberculin skin test (TST) and interferon-gamma release assay (IGRA), focusing on factors related to test discordance. MATERIALS AND METHODS: TST was administered to 1047 local and 900 migrant students; all migrants also received IGRA. TST cutoffs of 5 mm and 10 mm were applied. Agreement was measured using Cohen's Kappa, and determinants of discordance were analyzed with binary logistic regression. RESULTS: < 0.001). The agreement between IGRA and TST-12 mm (k = 0.491) was higher than that observed for TST-10 mm (k = 0.466) and TST-5 mm (k = 0.356). Subgroup analyses across sex, residence, ethnicity, BMI, TB contact, and BCG history confirmed superior consistency for TST-12 mm. Individuals without BCG vaccination were less likely to show discordance between IGRA and TST-12 mm (OR = 0.32, 95% CI: 0.10-0.81). CONCLUSIONS: Using a 12 mm cutoff improves TST accuracy for students from high-burden areas. IGRA should be preferred for individuals with BCG vaccination history.