Factor/Category Odds ratio 95%CI Test
Grade of smear positivity 3+ 1.4 0.7-2.0 NS
  1+ or 2+ 1  
Chest X-ray Cavity Present 2.1 1.2-3.5 P<0.01
  Absent 1  
Duration of cough 2 months or over 1.2 0.7-2.0 NS
  Less than 2 months 1  
Duration of contact (hours) 100- 2.5 1.5-4.1 P<0.01
  -99 1  
 Space of contact
 (sq. meters)
-49 2.0 1.2-3.4 P<0.01
50- 1  
Table 6: Odds ratios of incidence of infection according to various factors (Multiple logistic regression analysis).