Rationale: The scope of treatment of latent tuberculosis infection (LTBI) in the United States and Canada is unknown. Identifying the types of clinics that administer such treatment and patients who receive it could guide resource utilization and improve treatment initiation and completion.

Objectives: Estimate the number of persons started on LTBI treatment; describe the types of clinics that treat LTBI.

Methods: The Tuberculosis Epidemiologic Studies Consortium, consisting of 19 United States and 2 Canadian sites, conducted a survey among clinics that initiated LTBI treatment for>or=10 patients in 2002.

Results: Study catchment areas from the 19 United States sites represented 8.6% of the United States population and 12.7% of all tuberculosis cases in 2000. An estimated 37,857 patients started LTBI treatment during 2002 at 244 clinics surveyed. Of these treatment starts, 29,970 (79%) occurred at general public health clinics; immigrant/refugee clinics (2,409; 6.4%) and correctional/detention facilities (2,325; 6.1%) were the next most common sites. Based on these data, United States tuberculosis case rates, and United States population data, the estimated total number of LTBI treatment starts in the United States was 291,000-433,000. When the 37,145 persons who initiated LTBI treatment in the United States were extrapolated to the entire United States population, with a 5% lifetime risk of tuberculosis without treatment, and 20-60% treatment effectiveness, approximately 4,000-11,000 tuberculosis cases were prevented in the United States.

Conclusions: LTBI treatment is initiated among a substantial number of persons in the United States and Canada, primarily in the public sector. Treatment of LTBI can significantly decrease the tuberculosis burden.