The prevention of active tuberculosis through the treatment of latent tuberculosis infection is a major element of the national strategy for eliminating tuberculosis in the United States. Targeted treatment for persons who are at the highest risk for reactivation tuberculosis will be needed to achieve this goal. A more precise assessment of the lifetime risk of reactivation tuberculosis, usually estimated at 5 to 10 percent, could help to identify patients who are at the highest risk and motivate them to complete treatment. Currently, the rate of completion of treatment is low.

Published reports were reviewed to obtain estimates of the risk of tuberculosis among persons with a positive tuberculin skin test. Using these data, I constructed a model to estimate the lifetime risk of tuberculosis among persons with specific medical conditions.

The lifetime risk of reactivation tuberculosis is 20 percent or more among most persons with induration of 10 mm or more on a tuberculin skin test and either human immunodeficiency virus infection or evidence of old, healed tuberculosis. The lifetime risk is 10 to 20 percent among persons with recent conversion of a tuberculin skin test and among most persons younger than 35 years of age who are receiving infliximab therapy and have induration of 15 mm or more on a tuberculin skin test. The risk is also 10 to 20 percent among children five years of age or younger who have induration of 10 mm or more on a tuberculin skin test.

Persons with these characteristics should be targeted for intensive efforts to ensure full treatment of latent tuberculosis. Improved rates of completion of treatment among such persons could help to eliminate tuberculosis in the United States.