Self-Study Modules on Tuberculosis
This is an archived document. The links are no longer being updated.
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
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
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?