Association of prevalence of tuberculin reactions with closeness of contact among household contacts of new smear-positive pulmonary tuberculosis patients

OBJECTIVES: Among household contacts of newly diagnosed smear-positive pulmonary tuberculosis (TB) patients, to examine the association of apparent tuberculosis transmission with the closeness and duration of contact. METHODS: Household contacts of newly diagnosed patients with smear-positive pulmonary TB were identified, as well as a healthy population sample. Household contacts were categorized into three groups based on closeness, regularity, and duration of contact with index cases. All subjects underwent tuberculin testing. RESULTS: Among the household contacts, 47 of 112 (42%) of very close/intimate contacts had positive tuberculin tests, compared to 121 of 356 (34%) close/regular contacts and 23 of 178 (13%) not close/sporadic contacts and 55 of 355 (16%) of a healthy population sample. CONCLUSIONS: Even among household contacts of smear-positive pulmonary TB patients, there were major differences in the proximity and duration of contact which were strongly associated with differences in the prevalence of positive tuberculin reactions.