Abstract:

Objective: To analyze latent tuberculosis infection (LTBI) and related factors in close contacts of pulmonary tuberculosis patients. Methods: Tuberculosis patients (76 cases) and their close contacts (498 cases) registered and managed in Zhangjiagang City of Suzhou area from January 1 to December 31, 2021 were taken as research objects. The demographic characteristics and contact approaches of the research objects were investigated, and LTBI was determined by tuberculin skin test. The non-conditioned Binary Logistic stepwise regression model was used to screen the influencing factors of LTBI among close contacts of tuberculosis patients, and a forest plot was drawn. Results: Among 498 subjects, there were 179 cases of LTBI, resulting in an infection rate of 35.94%. The LTBI rate of close contacts of etiologically positive patients (37.64%, 172/457) was significantly higher than that of etiologically negative patients (17.07%, 7/41; χ²=6.910, P<0.001). Multivariable analysis showed that compared with the lowest three quartiles of age (<20 years) as the reference, the OR (95%CI) values of the risk of LTBI among close contacts of tuberculosis patients aged 20-39 years and ≥40 years were 1.768 (1.132-2.763) and 2.020 (1.093-3.733), respectively, showing an increasing trend of infection risk with increasing age ( {\chi }_{\mathrm{t}\mathrm{r}\mathrm{e}\mathrm{n}\mathrm{d}}^2=15.743, P<0.001). The infection risk of LTBI among non-family close contacts was 2.892(95%CI: 1.673-4.999) times of that of family close contacts. Conclusion: The LTBI rate among close contacts of tuberculosis patients in Zhangjiagang City, Suzhou area was relatively high. Close contacts of patients with etiologically positive pulmonary tuberculosis, close contacts aged 40 years and older, and non-family close contacts were at high risk of LTBI, and targeted preventive medication interventions should be carried out.

Key words: Tuberculosis, pulmonary, Contact tracing, Tuberculin, Skin tests, Factor analysis, statistical