Underestimated latent tuberculosis infection burden among school contacts in China: a cross-sectional study

Background: Previous research has indicated a low tuberculin skin tests (TST) strong positive rate in school tuberculosis (TB) screening implemented by community-level medical and health care institutions in China. The research objective was to evaluate the latent tuberculosis infection (LTBI) detection gap in school contact investigation in China.

Methods: In this cross-sectional study, school contacts were investigated by Chongqing Municipal Institute of Tuberculosis between January 2022 and April 2024 in Chongqing, China. TST, creation tuberculin skin test (C-TST), or Interferon-gamma release assays (IGRA) were conducted for immunological diagnostic methods. The LTBI detection gap among school contacts was assessed by comparing with the data implemented by community-level medical and health care institutions from 2021 to 2022.

Results: In 6063 participants, 4233 were tested using TST, 1799 were tested using C-TST, and 31 were tested using IGRA. Seven students were confirmed to have active TB. The LTBI prevalence rate using TST and C-TST was 15.2% (95%CI, 14.1-16.3%) and 3.6% (95%CI, 2.7-4.4%) respectively. A LTBI detection gap of 10.3% was identified when comparing with TST results implemented by community-level medical and health care institutions (χ² = 636, P < 0.001).

Conclusions: TB school contact investigation plays an important role in controlling TB epidemic. However, there may be a LTBI detection gap, likely due to poor quality control of TST implemented by community-level medical and health care institutions.