Which of the following tests is used for newborn screening in diagnosing Cystic Fibrosis?

The Immunoreactive Trypsin Level (IRT) test is a crucial component of newborn screening for cystic fibrosis. This test measures the amount of IRT in a newborn's blood. Elevated levels of IRT can indicate cystic fibrosis, as this condition often leads to pancreatic dysfunction, which in turn causes an increase in IRT.

Newborns are routinely screened for cystic fibrosis shortly after birth, and the IRT test serves as a reliable initial screening tool. If the IRT levels are elevated, further confirmatory tests, such as the sweat chloride test or genetic testing, may be performed to definitively diagnose cystic fibrosis.

While genetic testing can confirm a diagnosis by identifying mutations in the CFTR gene, it is not used as the first-line screening method for newborns because it doesn't detect all cases of cystic fibrosis and may miss cases that haven't yet manifested clinically. The sweat chloride test, though a standard confirmatory test for cystic fibrosis, is typically done after an elevated IRT result. A chest X-ray is not a screening test for cystic fibrosis and does not provide the diagnostic information related to the condition itself. Instead, it may be used to evaluate lung status after a diagnosis is confirmed.

Overall, the