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

Migrant students had higher TST positivity than locals (28.89% vs. 19.67%, p < 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.