Cystic Fibrosis Screening for Children

Cystic fibrosis is an inherited condition. A child is considered to be a “carrier” if he or she has inherited one normal copy of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and one abnormal, or mutated, copy. A carrier usually doesn’t develop symptoms of cystic fibrosis.

If your child has been diagnosed with cystic fibrosis, he or she has inherited two abnormal CFTR genes, one from each parent.

There is no way to prevent cystic fibrosis, but in recent years routine genetic screening, which can take place during pregnancy or immediately after birth, as well as screening in newborns, has led to dramatic improvements in care for people with this condition.

Screening has also improved long-term survival rates, as children with the condition can be identified and treated before symptoms develop. Research shows that children who receive a diagnosis and treatment early in life are healthier than those who are diagnosed later.

NYU Langone is the lead member of the New York State Newborn Screening Consortium, a select group of cystic fibrosis care centers that has received funding from the national Cystic Fibrosis Foundation. We are developing a statewide quality improvement program and are creating educational materials for parents to ease their anxiety about newborn and genetic screening tests.

Prenatal Genetic Screening

If both you and your partner are cystic fibrosis carriers or have a family history of the condition and are expecting a baby, you can find out if your unborn child has inherited any abnormal CFTR genes. Two commonly used prenatal tests, amniocentesis and chorionic villus sampling, are equally accurate in identifying CFTR mutations. NYU Langone genetic counselors can help you understand the results of these tests.

Amniocentesis

In an amniocentesis, the doctor inserts a hollow needle through a pregnant woman’s abdomen and into the uterus, removing a small amount of the amniotic fluid that surrounds the baby. A pathologist tests the fluid to look for abnormal CFTR genes.

Chorionic Villus Sampling

In a chorionic villus sampling test, experts analyze a small tissue sample from the placenta, which carries oxygen and nutrients from a mother to her baby. The doctor threads a thin tube through the vagina and cervix into the placenta to remove the tissue sample, which is then tested to see if it contains abnormal CFTR genes.

Bowel Imaging in Infants

As many as 20 percent of newborns with cystic fibrosis have difficulty passing their first stool because mucus in the digestive tract is too thick. This condition can lead to a blockage in the baby’s small intestine, called meconium ileus.

Occasionally, routine ultrasound tests performed during pregnancy may suggest a blockage in the small intestine. If your doctor suspects this, additional ultrasound scans may be performed later in the pregnancy to determine if the blockage has persisted or if it has resolved on its own. Immediately after the baby is born, an ultrasound or X-ray is performed to accurately diagnose meconium ileus.

Newborn Screening

Healthcare providers screen newborns for cystic fibrosis and several other conditions via a blood test while the baby is still in the hospital. This blood test is mandatory for all babies born in New York State and usually occurs when the infant is one day old.

A few drops of the baby’s blood, taken from a heel prick, are placed on a special card that is sent to a New York State Department of Health laboratory. The laboratory looks for a protein made in the pancreas called immunoreactive trypsinogen. During the first three weeks of life, infants with cystic fibrosis tend to have high levels of this protein. However, immunoreactive trypsinogen levels can also be high for other reasons, such as in babies who are born prematurely or those who have had a stressful delivery.

Results of the newborn screening test are usually available in about a week. If the baby’s blood sample contains a higher-than-average level of immunoreactive trypsinogen, the laboratory uses the same sample to look for 40 of the most common CFTR gene mutations that can lead to cystic fibrosis. The newborn screening test result is positive if the laboratory detects a high level of immunoreactive trypsinogen and two CFTR mutations.

A positive newborn screening test does not mean that your baby has cystic fibrosis. In fact, many babies who have a positive screening test do not have cystic fibrosis. All babies with a positive cystic fibrosis screening test are referred to a Cystic Fibrosis Foundation–accredited care center, such as NYU Langone, for a sweat test—a more sensitive test used to confirm or rule out a diagnosis of cystic fibrosis.

As a result of genetic sequencing of the cystic fibrosis gene done during newborn screening, it is possible to detect infants who have two CFTR mutations that may not cause cystic fibrosis. These children may have a normal or borderline sweat test result.

Rather than diagnosing these children with cystic fibrosis, our experts may diagnose a child with cystic fibrosis-related metabolic syndrome (CRMS) or cystic fibrosis screen positive, inconclusive diagnosis (CFSPID). Although these children do not have cystic fibrosis and do not require treatment, we recommend that they receive monitoring at our Pediatric Cystic Fibrosis Center because they may be at risk for developing cystic fibrosis in the future.

We understand that you may feel anxiety if you receive an abnormal screening test result for your newborn. Our Pediatric Cystic Fibrosis Center offers sweat testing at Hassenfeld Children’s Hospital, so you can get the answers you need as quickly as possible.