Final answer:
Useful tests for a nodule include skin testing and the tuberculin test. Skin testing is used to identify allergens in type I hypersensitivity, while the tuberculin test is used to test for delayed hypersensitivity related to tuberculosis.
Step-by-step explanation:
Useful tests for a nodule include skin testing and the tuberculin test. Allergists use skin testing, where allergen extracts are injected into the skin, to identify allergens in type I hypersensitivity. A positive result is indicated by a soft, pale swelling at the site surrounded by a red zone. The tuberculin test, on the other hand, is used to test for delayed hypersensitivity, specifically for tuberculosis. Bacterial proteins from M. tuberculosis are injected into the skin, and a few days later, a positive test is indicated by a raised red area that is hard to the touch.