Tuberculosis Testing and Treatment of Latent Infection

Abstract

Worldwide, there are more than 8 million new cases of Mycobacterium tuberculosis (TB) and 3 million deaths each year. In the United States, approx 15 million people are infected with TB. In 1965, shortly after isoniazid was found to be effective for the treatment of TB, the first recommendation for treating latent M. tuberculosis infection (LTBI) in the general population was given. The American Thoracic Society recommended that all persons with evidence of previously untreated TB, with recent tuberculin test conversions, and all children younger than 3 yr of age with a positive tuberculin skin test (TST) should be treated with isoniazid. Despite broadened recommendations in 1967 and a more widespread number of people being treated with an inexpensive drug that was thought to have few side effects, the morbidity from TB never dramatically fell as had been projected. When the hepatotoxicity of isoniazid began to be recognized in the early 1970s a controversy erupted over what would be the appropriate age cutoff in low-risk people that would ensure the benefits of therapy for LTBI and outweigh the risks of treatment. Rifampin (RIF) was introduced for the treatment of LTBI in the early 1980s because the real and perceived problems with isoniazid’s hepatotoxicity and the long period of treatment required with isoniazid had impaired isoniazid’s widespread usefulness.