Evaluation of application of 6-person dose recombinant Mycobacterium Tuberculosis fusion protein skin test in screening close contacts of pulmonary tuberculosis cases in schools

Objective To evaluate the effectiveness of the multi-dose recombinant Mycobacterium tuberculosis fusion protein (EC) skin test in screening M, tuberculosis infection, and provide data support for its application in screening key population.

Methods The close contacts of tuberculosis cases in students were selected from 11 school with tuberculosis epidemics in Pudong New Area, Shanghai, from August 2023 to February 2024 as study participants. Each participant underwent both EC skin test and γ-interferon release test (IGRA, using T-SPOT.TB) for the detection of M. tuberculosis infection. For the EC skin test, 0.1mL/person was drawn form a 1.0mL/vial preparation, and administered using a 6-person inoculation method. In the statistical analysis, χ² test was used to compare the difference, and Kappa coefficient was used to evaluate the consistency between the two methods.

Results A total of 463 study participants were included, including 212 men and 251 women; 304 college students, 124 middle school students and 35 teachers. The positive rate of EC skin test was 4.54% (21/463), and the positive rate of IGRA test was 10.37% (48/463), the difference was significant(χ²=117.945, P<0.001).The Kappa coefficient for consistency between the two detection methods was 0.46 (t=3.478, P<0.001); Using the IGRA infection test results as the reference standard, the sensitivity of the EC skin test was 35.42% (95% CI: 23.43%−49.57%), the specificity was 99.04% (95%CI: 97.55%−99.63%), the positive prediction value was 80.95% (95% CI: 60.00%−92.34%), negative predicted value was 92.99%(95% CI: 90.22%−95.00%), and the Youden index was 0.35. The differences in EC positive rate among the study participants with different demographic characteristics had no significance.

Conclusion The effectiveness of EC shin test (administered at 1.0 mL/vial for six recipients) for M. tuberculosis infection screening in schools still requires further evaluation by expanded screening and parallel-group controlled studies. Meanwhile, IGRA and chest CT examination should be considered as supplementary measures to cover populations with contraindications to EC vaccination.