Which test can be used to confirm a diagnosis of cystic fibrosis?

The sweat chloride test is the standard diagnostic tool for confirming cystic fibrosis. This test measures the concentration of chloride in sweat; individuals with cystic fibrosis have elevated levels of chloride due to a malfunction in the CFTR gene, which leads to impaired chloride transport in epithelial cells. This characteristic high concentration in sweat is a hallmark of cystic fibrosis and is used clinically to support a diagnosis after initial suspicion based on clinical symptoms or family history.

While other tests such as X-rays and bacterial cultures can provide information related to lung infections or structural problems, they do not specifically confirm cystic fibrosis. A blood test for specific antibodies might help in providing supplementary information but does not directly measure the characteristic physiological defect seen in cystic fibrosis. Therefore, the sweat chloride test remains the definitive method to confirm the diagnosis.