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Table 3 PTB status across the variables of interest

From: The risk of pulmonary tuberculosis in underground copper miners in Zambia exposed to respirable silica: a cross-sectional study

Characteristics PTB cases
(n = 34)
No PTB
(n = 323)
Age at certification, years, Mean, (SD) a* 34 (6.0) 31.0 (6.2)
Smoking statusb
 Non-smokers, n, (%) 22 (64.7) 273 (84.5)
 Current smokers, n, (%)** 12 (35.3) 39 (12.1)
Length of service, Mean, (SD) a* 6.1 (2.0) 5.1 (2.5)
Sex
 Male, n, (%) 34 (9.5) 323 (90.5)
Cumulative respirable silica Dust Exposure, Mean, (SD) a** 2.2 (1.0) 1.5 (0.9)
Cumulative respirable silica dust categoriesb
 Low, n, (%) 3 (8.8) 116 (35.9)
 Medium, n, (%)* 10 (29.4) 105 (32.5)
 High, n, (%)** 21 (61.8) 102 (31.6)
  1. *p-value < 0.05; ** p-value < 0.01
  2. at-test
  3. bChi-square test