Abstract:

Objective: By investigating the incidence and characteristics of tuberculin skin test (tuberculin skin test,TST) and active tuberculosis in close contacts of pulmonary tuberculosis patients in schools, to provide basic data for the prevention and control of tuberculosis in schools. Methods: In this paper, a cohort study was used to research 307 close contacts of students (excluding 19 transfer scholars) from a school in Yiyang County, Luoyang City, He’nan Province during the epidemic treatment from March 2019 to May 2021 as the subjects of baseline screening, and 300 close contacts of students (excluding 7 active tuberculosis patients found in the baseline screening) as the subjects of two-year follow-up cohort study, including suspicious symptom screening, TST test, and chest X-ray examination. The incidence rate of tuberculosis, the strong positive prevalence of TST and the strong positive conversion rate of TST were observed at different follow-up stages. Results: A total of 119 TST strongly positive patients were found during the 2-year follow-up cohort survey. The strong positive prevalence of TST were 26.06% (80/307), 33.45% (99/296), 39.64% (111/280), 40.71% (114/280), 42.09% (117/278) and 43.12% (119/276) with the baseline screening and five follow-up screening. The difference between the strong positive prevalence of TST for baseline screening and the previous two follow-up screenings (two months before ultraviolet disinfection in September 2019) was statistically significant (χ²=6.261, P=0.044). A total of 75 students with strong positive conversion rate of TST were found in the five follow-up screenings, and the positive conversion rate was 18.92% (42/222), 9.47% (16/169), 4.05% (6/148), 4.20% (6/143) and 3.73% (5/134), respectively, among which the difference in the positive conversion rate of the first and second follow-up screening was statistically significant (χ²=5.097, P=0.024). A total of 28 patients with active pulmonary tuberculosis were found in the five follow-up screenings, and the incidence rate was 5.00/100 person years (28/560.22 person years). The incidence of 77 TST strongly positive patients diagnosed with tuberculosis during follow-up (9.47/100 person-years, 13/137.23 person years) at baseline was significantly higher than the incidence of 214 TST negative patients at baseline (3.70/100 person-years, 15/404.99 person years), with a statistically significant difference (χ²=6.143, P=0.013). The 85 students with strong positive TST and completed the whole course of preventive treatment had no disease, and there was a statistically significant difference in the incidence rate (21.14/100 person years,17/80.41 person years) of 51 students strongly positive for TST without preventive treatment (26 students) and completed the full course of preventive treatment (25 students)(χ²=31.820, P=0.000). Conclusion: Close contacts of school tuberculosis patients have a high risk of cluster infection, and it is necessary to screen close contacts of pulmonary tuberculosis during the infection period and window period for suspected symptoms, TST and chest X-ray examination for multiple times, and those TST strong positive students should receive active preventative anti-tuberculosis treatment.

Key words: Student, Tuberculosis, pulmonary, Contact tracing, Cohort studies, Follow-up studies