A nurse is caring for a child who has a suspected diagnosis of cystic fibrosis. Which of the following diagnostic tests will confirm the diagnosis?

The correct answer is Choice D.Choice A rationaleA sputum culture can help identify respiratory infections but is not definitive for diagnosing cystic fibrosis.Choice B rationaleStool fat content analysis can indicate malabsorption issues but is not specific to cystic fibrosis.Choice C rationalePulmonary function tests assess lung function but do not confirm a diagnosis of cystic fibrosis.Choice D rationaleThe sweat chloride test is the gold standard for diagnosing cystic fibrosis. It measures the concentration of chloride in sweat, which is elevated in individuals with cystic fibrosis due to defective chloride transport in sweat glands. .