Which test is considered an alternative to the sweat test for screening cystic fibrosis?

The immunoreactive trypsin test is recognized as an alternative screening method for cystic fibrosis. This test measures the level of immunoreactive trypsinogen, a protein that is produced by the pancreas and often elevated in newborns with cystic fibrosis. When this test is conducted shortly after birth, a high level of immunoreactive trypsinogen can indicate a higher likelihood of cystic fibrosis, prompting further diagnostic testing, such as the sweat test.

In contrast, genetic screening focuses on detecting specific mutations in the CFTR gene that causes cystic fibrosis, and while it can confirm the diagnosis, it is not primarily used as a screening tool. The meconium test, while also relevant to diagnosing cystic fibrosis, particularly in infants, is not a primary screening method like the immunoreactive trypsin test. Lastly, a chest X-ray is primarily used to evaluate lung conditions and would not provide a specific indication of cystic fibrosis in the absence of other symptoms. Therefore, the immunoreactive trypsin test stands out as a practical alternative screening tool for this condition.