A nurse is caring for a school-age child who underwent a tuberculin skin test 3 days ago and has a 3-mm induration at the test site. The nurse should identify this finding as which of the following?

Interpreting a tuberculin skin test requires knowledge of immunology and the criteria for induration size. One must apply standardized health guidelines to differentiate between positive and negative results based on the measurement of the delayed-type hypersensitivity reaction. Choice A rationale An allergic reaction would typically manifest as immediate redness or itching. The tuberculin test measures a delayed T-cell mediated response. A 3-mm induration is a specific measurement of that response, not a general allergy. Choice B rationale For a child with no known high-risk factors, an induration of less than 10 mm is considered a negative result. A 3-mm area of hardness does not meet the diagnostic threshold for a positive Mantoux test. Choice C rationale Active tuberculosis is diagnosed through chest X-rays, sputum cultures, and clinical symptoms like night sweats or hemoptysis. A 3-mm induration is insufficient to diagnose any form of the disease, especially at that small size. Choice D rationale Disseminated disease involves the spread of tuberculosis to multiple organs. This would be associated with a strong positive skin test or anergy in severe cases, but a 3-mm induration is simply a negative screening finding.