Neonatal cystic fibrosis screening test
Cystic fibrosis screening - neonatal; Immunoreactive trypsinogen; IRT test; CF - screening
Neonatal cystic fibrosis screening is a blood test that screens newborns for cystic fibrosis (CF).
Parents can pass all kinds of different traits to their children, from blue eyes to blonde hair. Sometimes, parents can also pass the genes for certain diseases to their kids. Cystic fibrosis is one very serious inherited disease that makes it hard for children to breathe and digest food. Let's talk about cystic fibrosis. Genes are the coded instructions that tell our bodies how to operate. Usually, the code is correct and everything runs smoothly. But sometimes, the code is incorrect because of a defective gene or genes. In the case of cystic fibrosis, a faulty gene causes the body to produce an abnormally thick, sticky fluid called mucus. This mucus clogs the lungs, making it hard to breathe. It also gets stuck in the pancreas, making it harder for the body to break down and digest food. Millions of Americans carry the cystic fibrosis, or CF gene. Fortunately, most of them don't have cystic fibrosis. That's because you need to inherit one faulty gene from each parent to actually get the disease. Kids who are born with cystic fibrosis start showing signs very early. Newborns don't grow or gain weight as quickly as they should, and they don't make bowel movements because their bodies aren't digesting food properly. As these children get older, they may have symptoms like coughing and fatigue from the mucus in their lungs, and nausea and stomach pain from the mucus in their pancreas. They'll also get pneumonia and other lung infections more often than normal. So, you may now be asking, how do you know if your child has cystic fibrosis? Doctors diagnose cystic fibrosis using a blood test that looks for the CF gene. There is also a sweat test, which looks for saltier-than-normal sweat, another symptom of cystic fibrosis. Doctors may use other tests, such as a chest x-ray or upper GI series, to check for lung and bowel problems caused by CF. It's a good idea to get treated at a center that specializes in cystic fibrosis because they're up on all the latest therapies. For lung problems, treatments include inhaled medicines to open the airways, medicine to thin mucus and make it easier to cough up, and antibiotics to prevent lung infections. Some people may eventually need a lung transplant. For bowel problems, you'll need to eat a special diet that's higher in protein and calories to make up for the nutrients you're losing. You may also take vitamin supplements. The outlook for people with cystic fibrosis is better today than ever before. Thanks to new treatments, people with this disease can live well into adulthood. They can go to school, play sports, and get a job like everyone else. But because the symptoms of cystic fibrosis are so serious, it's very important to stay on top of treatment, and to call the doctor right away if symptoms get worse. Anyone with a family history of the disease may want to get screened for the CF gene before they decide to have children.
How the Test is Performed
A sample of blood is either taken from the bottom of the baby's foot or a vein in the arm. A tiny drop of blood is collected onto a piece of filter paper and allowed to dry. The dried blood sample is sent to a lab for analysis.
The blood sample is examined for increased levels of immunoreactive trypsinogen (IRT). This is a protein produced by the pancreas that is linked to CF.
How the Test will Feel
The brief feeling of discomfort will probably cause your baby to cry.
Why the Test is Performed
Cystic fibrosis is a disease passed down through families. CF causes thick, sticky mucus to build up in the lungs and digestive tract. It can lead to breathing and digestive problems.
Children with CF who are diagnosed early in life and start treatment at a young age may have better nutrition, growth, and lung function. This screening test helps doctors identify children with CF before they have symptoms.
Some states include this test in the routine newborn screening tests that are done before the baby leaves the hospital.
If you live in a state that does not perform routine CF screening, your health care provider will explain whether testing is needed.
Other tests that look for genetic changes known to cause CF may also be used to screen for CF.
If the test result is negative, the child likely does not have CF. If the test result is negative but the baby has symptoms of CF, further testing will likely be done.
What Abnormal Results Mean
An abnormal (positive) result suggests that your child may have CF. But it is important to remember that a positive screening test does not diagnose CF. If your child's test is positive, more tests will be done to confirm the possibility of CF.
- Sweat chloride test is the standard diagnostic test for CF. A high salt level in the person's sweat is a sign of the disease.
- Genetic testing may also be done.
Not all children with a positive result have CF.
Risks associated with the test include:
- Infection (a slight risk any time the skin is broken)
- Anxiety over false positive results
- False reassurance over false negative results
Egan ME, Schechter MS, Voynow JA. Cystic fibrosis. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 432.
Lo SF. Laboratory testing in infants and children. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 747.
Last reviewed on: 5/27/2020
Reviewed by: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.