Newborn Screening for Cystic Fibrosis in the United States: Blood Tests and Genetic Testing explained
Summary
- Cystic fibrosis is a genetic disorder that affects the lungs and digestive system
- Newborn screening for cystic fibrosis in the United States involves testing for elevated levels of immunoreactive trypsinogen (IRT)
- Positive results from newborn screening are followed up with Genetic Testing to confirm a diagnosis of cystic fibrosis
Introduction
Cystic fibrosis is a genetic disorder that affects the lungs and digestive system. It is caused by mutations in the CFTR gene, which is responsible for producing a protein that helps control the flow of salt and fluids in and out of cells. In the United States, newborns are routinely screened for cystic fibrosis shortly after birth to allow for early intervention and treatment. This article will explore the specific blood tests used to screen newborns for cystic fibrosis in the United States.
Immunoreactive Trypsinogen (IRT) Testing
One of the primary blood tests used to screen newborns for cystic fibrosis in the United States is the measurement of immunoreactive trypsinogen (IRT) levels. IRT is a protein that is produced by the pancreas and is normally found in small amounts in the blood. However, in infants with cystic fibrosis, the CFTR gene mutation can cause an increase in IRT levels in the blood.
The IRT test is typically performed by collecting a few drops of blood from a newborn's heel shortly after birth. The blood sample is then analyzed in a laboratory to measure the level of IRT present. If the IRT level is elevated, it may indicate that the newborn has cystic fibrosis and additional testing is warranted.
Sweat Chloride Test
In addition to IRT testing, newborns who have elevated levels of IRT may undergo a sweat chloride test to confirm a diagnosis of cystic fibrosis. The sweat chloride test is considered the gold standard for diagnosing cystic fibrosis and involves collecting a sample of sweat from the skin to measure the amount of chloride present.
Individuals with cystic fibrosis have abnormally high levels of chloride in their sweat due to the dysfunctional CFTR protein. A positive result on the sweat chloride test, in combination with elevated IRT levels, is highly indicative of cystic fibrosis and may prompt further Genetic Testing to identify specific mutations in the CFTR gene.
Genetic Testing
Once a newborn has been identified as having elevated IRT levels and a positive sweat chloride test, Genetic Testing is often performed to confirm a diagnosis of cystic fibrosis. Genetic Testing involves analyzing the CFTR gene to identify specific mutations that are known to cause the disorder.
There are hundreds of different mutations in the CFTR gene that can lead to cystic fibrosis, and Genetic Testing can help determine which mutations are present in an individual with the disease. This information is important for guiding treatment decisions and providing genetic counseling to the affected individual and their family members.
Conclusion
In conclusion, newborn screening for cystic fibrosis in the United States involves a combination of blood tests, including immunoreactive trypsinogen (IRT) testing and the sweat chloride test. Positive results from these tests are followed up with Genetic Testing to confirm a diagnosis of cystic fibrosis and identify specific mutations in the CFTR gene. Early detection and intervention are crucial for improving outcomes for individuals with cystic fibrosis, and newborn screening plays a vital role in ensuring that affected individuals receive the care they need.
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