Should young adults with a positive tuberculin test take isoniazid?

We used decision analysis to determine the benefits and risks of preventive therapy with isoniazid for young adults whose only risk factor for the development of active tuberculosis was a positive tuberculin skin test. We assumed that the risk of developing active tuberculosis over the next 20 years ranged from 0.56% to 1.30% for such persons; that isoniazid can reduce this risk by 30% to 70%; and that the risk of developing isoniazid-related hepatitis ranged from 0.3% to 1.1%. Among 100 000 such persons, treatment with isoniazid could prevent from 168 to 910 cases of tuberculosis over 20 years. However, from 300 to 1100 cases of isoniazid-related hepatitis would occur in the year of treatment. The benefits of preventive therapy in this group do not appear clearly to outweigh the risks. We disagree with the recommendation of the American Thoracic Society and the Centers for Disease Control that all such patients take isoniazid.