"Clinicians who care for people with HIV/AIDS should take note of this important finding," says NIAID Director Anthony S. Fauci, M.D. "This study suggests that we can make more efficient use of TB prevention resources by focusing on HIV-infected persons with known TB infection or who have close contact with another individual with active TB."
Although only 10 percent of healthy people infected with TB bacteria ever develop active TB disease, co-infection with TB and HIV dramatically increases this risk. A number of studies have shown that daily treatment with the antibiotic isoniazid (INH) significantly reduces TB disease risk in persons known to be co-infected with HIV and TB.
The tuberculin skin test, which involves injecting TB-derived proteins below the skin, is the only method available for diagnosing inactive, or latent, TB infection. Palpable swelling at the site of injection occurs in most TB-infected people with healthy immune systems. However, HIV-infected people with suppressed immune systems often exhibit anergy, a reduced or absent reaction to skin tests for TB as well as other infections. In such persons, TB infection can be masked by a false negative skin test. As a precaution against activation of a possible latent TB infection, in 1991 the Centers for Disease Control and Prevention (CDC) suggested that INH preventive therapy be given to anergic HIV-infected individuals at high risk for TB. High-risk individuals include those who belong to groups, such as homeless persons and those who inject drugs, in which the prevalence of TB infection is at least 10 percent.
To determine the effectivene
Contact: John Bowersox
NIH/National Institute of Allergy and Infectious Diseases