A client with a positive Mantoux test result will be sent for a chest x-ray. For which of the following reasons is this done?
A. To confirm the diagnosis.
B. To determine if a repeat skin test is needed.
C. To determine the extent of the lesions.
D. To determine if this is a primary or secondary infection.
Correct Answer: C. To determine the extent of the lesions.
If the lesions are large enough, the chest x-ray will show their presence in the lungs. A positive Mantoux test indicates exposure to tuberculosis or latent tuberculosis. However, this test lacks specificity, and patients require subsequent visits to interpret the result and a chest x-ray for confirmation of the disease.
Option A: Sputum culture confirms the diagnosis. Mycobacterial culture is the gold standard for diagnosis. Mycobacterial culture should be performed on both the solid and liquid medium. Liquid media culture can detect very low bacterial load and is considered a gold standard. Culture essential for drug susceptibility testing.
Option B: There can be false-positive and false-negative skin test results. Although the test is considered relatively sensitive, false-positive results are seen with BCG vaccination. The Mantoux test should never be regarded as a confirmatory test.
Option D: A chest x-ray can’t determine if this is a primary or secondary infection. Apart from these, Tuberculin skin testing and/or interferon-gamma release assay should be performed depending on the situation. These tests should not be wholly relied upon in the diagnosis of active tuberculosis, but assist in diagnosis.
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