The tuberculosis skin test (also known as the tuberculin or PPD test) determines whether a person has developed an immune response to the bacterium that causes tuberculosis (TB).
The predictive value of the skin prick test weal size for the outcome of oral food challenges". Clin. Exp. Allergy 35 (9): 1220–6. doi: 10.1111/j.1365-2222.2005.2324.x.