Evaluation of investigations conducted to detect and prevent transmission of tuberculosis

Abstract

Context: Contact investigations are routinely conducted by health departments throughout the United States for all cases of active pulmonary tuberculosis (TB) to identify secondary cases of active TB and latent TB infection and to initiate therapy as needed in these contacts. Little is known about the actual procedures followed, or the results.

Objectives: To evaluate contact investigations conducted by US health departments and the outcomes of these investigations.

Design, setting, and subjects: Review of health department records for all contacts of 349 patients with culture-positive pulmonary TB aged 15 years or older reported from 5 study areas in the United States during 1996.

Main outcome measures: Number of contacts identified, fully screened, and infected per TB patient; rates of TB infection and disease among contacts of TB patients; and type and completeness of data collected during contact investigations.

Results: A total of 3824 contacts were identified for 349 patients with active pulmonary TB. Of the TB patients, 45 (13%) had no contacts identified. Of the contacts, 55% completed screening, 27% had an initial but no postexposure tuberculin skin test, 12% were not screened, and 6% had a history of prior TB or prior positive tuberculin skin test. Of 2095 contacts who completed screening, 68% had negative skin test results, 24% had initial positive results with no prior test result available, 7% had documented skin test conversions, and 1% had active TB at the time of investigation. Close contacts younger than 15 years (76% screened vs 65% for older age groups; P<.001) or exposed to a TB patient with a positive smear (74% screened vs 59% for those with a negative smear; P<.001) were more likely to be fully screened. Close contacts exposed to TB patients with both a positive smear and a cavitary chest radiograph were more likely to have TB infection or disease (62% vs 33% for positive smear only vs 44% for cavitary radiograph only vs 37% for neither characteristic; P<.001). A number of factors associated with TB patient infectiousness, contact susceptibility to infection, contact risk of progression to active TB, and amount of contact exposure to the TB patient were not routinely recorded in health department records.

Conclusions: Improvement is needed in the complex, multistep process of contact investigations to ensure that contacts of patients with active pulmonary TB are identified and appropriately screened.