The nurse performs an admission assessment on a client with a diagnosis of tuberculosis. The nurse should check the results of which diagnostic test that will confirm this diagnosis?

A. Sputum culture for AFB: A sputum culture for acid-fast bacilli (AFB) is the definitive diagnostic test for active tuberculosis. It confirms the presence of Mycobacterium tuberculosis by identifying and culturing the bacteria from sputum, which is the most reliable confirmation of disease. B. Chest x-ray: A chest x-ray can show lung abnormalities consistent with TB, such as cavitations or infiltrates, but it cannot confirm active infection. It is useful for supporting diagnosis but must be interpreted alongside microbiological tests. C. Mantoux test: The Mantoux (PPD) test identifies TB exposure by measuring delayed hypersensitivity, but it does not distinguish between latent and active infection. A positive result requires further testing to confirm active disease. D. Pulmonary function test: Pulmonary function tests assess lung capacity and airflow but are not used for diagnosing tuberculosis. They may be used later to evaluate lung impairment but have no role in confirming TB.