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Education Materials > Publications > Self-Study Modules on TB > Module 3 > Diagnosis of TB > Chest X-Ray

Self-Study Modules on Tuberculosis

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Module 3: Diagnosis of Tuberculosis Infection and Disease

The Chest X-Ray

The chest x-ray is useful for diagnosing TB disease because about 85% of TB patients have pulmonary TB (TB disease in the lungs). Usually, when a person has TB disease in the lungs, the chest x-ray appears abnormal (Figure 3.6). It may show infiltrates (collections of fluid and cells in the tissues of the lung) or cavities (hollow spaces within the lung that may contain many tubercle bacilli).

Figure 3.6 Abnormal chest x-ray. Arrow points to cavity in patientís right upper lobe. Left lobe is normal. This is a picture of an abnormal chest x-ray. There is an arrow that points to a cavity in the patientís right upper lobe. The left lobe is normal.

The purposes of the chest x-ray are to

  • Help rule out the possibility of pulmonary TB disease in a person who has a positive reaction to the tuberculin skin test
  • Check for lung abnormalities in people who have symptoms of TB disease

However, the results of a chest x-ray cannot confirm that a person has TB disease. A variety of illnesses may produce abnormalities whose appearance on a chest x-ray resembles TB. Although an abnormality on a chest x-ray may lead a clinician to suspect TB, only a bacteriologic culture that is positive for M. tuberculosis proves that a patient has TB disease. Moreover, a chest x-ray cannot detect TB infection.

In patients who are infected with HIV, pulmonary TB disease may have an unusual appearance on the chest x-ray. The chest x-ray may even appear entirely normal.

Study Questions 3.25-3.26

3.25. Name the two purposes of the chest x-ray.

3.26. Can the results of a chest x-ray confirm that a person has TB disease? Why or why not?



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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