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U.S. Department of Health and Human Services


Core Curriculum on Tuberculosis, 2000

Chapter 7
Treatment of TB Disease

Response to Treatment

For patients whose sputum cultures are positive before treatment, the best way to measure the effectiveness of therapy is to obtain specimens for culture at least monthly until the cultures convert to negative. Patients whose sputum no longer contains M. tuberculosis after 2 months of treatment should have at least one further sputum smear and culture performed at the completion of therapy. Patients with multidrug-resistant TB should have cultures performed monthly for the entire course of treatment. Radiographic evaluations during treatment are of less importance than sputum evaluation. However, a chest film at completion of treatment provides a baseline for comparison with any future films.

Patients whose cultures have not become negative or whose symptoms do not resolve despite 3 months of therapy should be reevaluated for potential drug-resistant disease, as well as for potential failure to adhere to the regimen. If the patient is receiving self-administered therapy, the remainder of treatment should be directly observed. While the results of drug susceptibility testing are pending, the original drug regimen may be continued or may be augmented by at least two drugs not given previously. Never add one drug at a time to a failing regimen; this may cause further drug resistance. If drug susceptibility results show resistance to any of the first-line drugs or if the patient remains symptomatic or smear or culture positive after 3 months, a TB medical expert should be consulted.

In patients with negative sputum cultures before treatment, the major indicators of response to therapy are the chest radiograph and the clinical evaluation. The intervals at which chest radiography should be repeated depend on the clinical circumstances and the differential diagnosis that is being considered, but usually no more than every 3 months. If the radiograph does not improve after the patient has received 3 months of treatment, the abnormality may be the result of either previous (not current) TB or another process.

Routine follow-up after therapy is not necessary for patients who have had a satisfactory and prompt bacteriologic response to 6- or 9-month therapy with both isoniazid and rifampin. Patients whose organisms were fully susceptible to the drugs being used should be instructed to promptly report the development of any symptoms, particularly prolonged cough, fever, or weight loss. For patients with organisms resistant to isoniazid or rifampin or both, follow-up evaluation must be individualized.


Released October 2008
Centers for Disease Control and Prevention
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
Division of Tuberculosis Elimination -

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