The tuberculin skin test is used to determine past or present infection with which disease based on a positive skin reaction?

• A. Malaria
• B. Dengue
• C. Tuberculosis
• D. Influenza

Answer: (C)

The tuberculin skin test is about detecting exposure to tuberculosis. It works by injecting a small amount of tuberculin under the skin and seeing if the immune system recognizes it. If there’s a positive skin reaction, it means you’ve been infected with Mycobacterium tuberculosis at some point, which could be a latent infection or active tuberculosis. The test doesn’t diagnose the disease itself; further evaluation is needed to determine if TB is active and to guide treatment.

This test isn’t used for malaria, dengue, or influenza, which are diagnosed in other ways. Factors like prior vaccination with BCG or exposure to non-tuberculous mycobacteria can affect interpretation, and sometimes the test can be falsely negative in people with weakened immune systems.