Screening for tuberculosis in health examination participants and clinical study on the spontaneous occurrence of tuberculosis in the populations with strong positive reaction to tuberculin skin test in ten years

Abstract

Objective To analyze the results of screening for tuberculosis (TB) in health examination participants and study the spontaneous occurrence of TB in the subjects with strong positive reaction to tuberculin skin test (TST) in ten years. Method Totally 12 598 health examination participants without past TB history were selected, of whom 8 896 were college students, 2 496 migrant workers and 1 206 had close contacts with active TB patients. They were screened by TST with strong positive reaction. All of subjects with TST strong positive results received chest X-ray examination and sputum acid-fast bacteria Result Thirty-seven cases were diagnosed as TB by TST screening, and the total detection rate was 0.29% (37/12 598). Among them 11 were college students (0.12%, 11/8 896), 12 were migrant workers (0.48%, 12/2 496) and 14 were close contacts (1.16%, 14/1 206) respectively. The detection rates were different among the three groups (χ2=31.40, P=0.000). Among 897 strong positive subjects, the strong positive rate was 7.12% (897/12 598), 316 were college students (3.55%, 316/8 896), 388 migrants workers(15.54%, 388/2 496), and 193 close contacts (16.00%, 193/1 206) respectively. There was significant difference in strong positive rate among the three groups (χ2=583.04, P=0.000), and the strong positive rate of college students was lower compared with that of the migrant workers and the close contacts (χ2=483.51 and 344.11, P<0.01). In ten years, 54 subjects were diagnosed as TB in 429 subjects with strong positive reaction to TST, the spontaneous cumulative incidence rate was 12.58% (54/429). Among them, the cumulative morbidity rate was 9.21% (14/152) in college students, 9.58% (18/188) in migrant workers and 24.72% (22/89) in close contacts respectively. The spontaneous morbidity rate of close contacts was higher than that of college students and migrant workers (χ2=10.63 and 11.21, P<0.001); 75 were lost in 398 participants, the dropout rate was 18.84% (75/398). In first three years of follow-up, 31 were diagnosed TB in 429 participants, the cumulative incidence rate was 7.23% (31/429). Of them 9 were college students (5.92%, 9/152), 10 migrant workers (5.32%, 10/188) and 12 close contacts (13.48%, 12/89) respectively (χ2= 6.60, P=0.037). In the fourth to tenth years of follow-up, 23 were diagnosed TB in 398 participants, the cumulative incidence rate was 5.78% (23/398), which was not significantly different compared with the cumulative incidence rate of the first three years (χ2=2.50, P=0.37). Tirty-seven patients received standard anti-tuberculosis drug therapy for one year, no one of them had recurrence at ten-year follow-up. Conclusion The migrant workers and close contacts are the high-risk populations for TB. All of them with strong positive response to TST results are susceptible to TB. So regular physical examination is recommended for them and health management should be strengthened. Key words: Tuberculin skin test; Tuberculosis, pulmonary; Cumulative incidence rate; Health management