Ten days after exposure to a patient with tuberculosis, a tuberculin skin test yields a positive result. The most likely interpretation is:

Ten days after exposure to a patient with tuberculosis, a tuberculin skin test yields a positive result. The most likely interpretation is:

• A. You are actively infected and should be treated immediately.
• B. You contracted the disease through casual contact.
• C. You were exposed to another infected person prior to treating the patient.
• D. The disease is dormant in your body.

Answer: (C)

A tuberculin skin test shows a delayed-type hypersensitivity to TB antigens, which reflects prior sensitization after TB infection or vaccination. After initial infection, the immune response typically needs about 2–8 weeks to become positive. Seeing a positive test ten days after this exposure is best explained by previous exposure to TB, meaning you were already exposed to an infected person before treating the current patient. This indicates prior infection (latent TB) rather than a new, active infection from the most recent exposure. Remember, a positive test does not prove active disease; it simply shows TB exposure or infection. To determine active TB, you’d assess symptoms and obtain imaging and microbiology.

A tuberculin skin test shows a delayed-type hypersensitivity to TB antigens, which reflects prior sensitization after TB infection or vaccination. After initial infection, the immune response typically needs about 2–8 weeks to become positive. Seeing a positive test ten days after this exposure is best explained by previous exposure to TB, meaning you were already exposed to an infected person before treating the current patient. This indicates prior infection (latent TB) rather than a new, active infection from the most recent exposure.

Remember, a positive test does not prove active disease; it simply shows TB exposure or infection. To determine active TB, you’d assess symptoms and obtain imaging and microbiology.