Which test result can be the only sign of latent TB infection?

Which test result can be the only sign of latent TB infection?

• A. Positive skin test
• B. Chest X-ray changes
• C. Fever
• D. Cough

Answer: (A)

Latent TB infection means the person is infected with TB bacteria but has no symptoms and no contagious disease. The only sign you might see without illness is an immunologic reaction to TB antigens. A positive tuberculin skin test shows that the immune system has been sensitized to TB and indicates infection, which is consistent with latent TB when there are no symptoms and the chest X-ray is normal. Fever or cough are symptoms of active TB, and chest X-ray changes usually reflect active disease or older TB lesions, not latent infection. So the positive skin test is the sign that can indicate latent TB infection by itself.

Latent TB infection means the person is infected with TB bacteria but has no symptoms and no contagious disease. The only sign you might see without illness is an immunologic reaction to TB antigens. A positive tuberculin skin test shows that the immune system has been sensitized to TB and indicates infection, which is consistent with latent TB when there are no symptoms and the chest X-ray is normal. Fever or cough are symptoms of active TB, and chest X-ray changes usually reflect active disease or older TB lesions, not latent infection. So the positive skin test is the sign that can indicate latent TB infection by itself.