When blood is taken from a newborn for screening, many parents ask me why this is done. I explain that there are a number of genetically determined diseases that can identified at birth. One of those that can now be identified is cystic fibrosis.

Christopher N. Fortner, MD, PhD, from Duke Children's pulmonary division, explains what newborn cystic fibrosis screening is and how it will help children in North Carolina.

-- Dennis Clements MD, PhD, MPH

Christopher N. Fortner, MD, PhD

The North Carolina State Laboratory of Public Health added a new test to its newborn screening tests in 2009. For all children born in North Carolina on April 13, 2009, or later, the state now screens for the disease called cystic fibrosis.

This new test is run on the same blood sample that the state collects on every child born in North Carolina.

What Is Cystic Fibrosis?

Cystic fibrosis (often abbreviated CF) is an inherited disease that can affect many different parts of the body. It is caused by a certain protein not functioning properly. This protein is normally found in epithelial cells, which are cells that line parts of the organs of the body.

Not everyone with CF has the same symptoms of the disease, but some of the most commonly affected organs are the airways, the digestive system, and sweat glands. When the CF protein does not work properly, it causes problems with water and salt balance at the cellular level.

Normal airway secretions often become thick, sticky mucous that makes it more likely for people with CF to develop bronchitis or sinus infections. Normal digestive juices that are produced in the pancreas also become sticky and no longer work to help absorb nutrients from food. The sweat glands of the skin produce sweat that is higher in salt content than sweat from people without CF.

Specialized therapies are often needed to help manage these problems so that children who have CF can live into adulthood. Patients with CF are often living into their 30s and beyond.

CF is a recessive genetic condition, meaning that babies must inherit two abnormal copies of the CF gene, one from each parent. If someone inherits one normal copy and one abnormal copy of the CF gene they do not have CF. There are hundreds of different mutations that lead to an abnormal CF gene.

People of all races can have CF, but it is more common in white people, especially those with northern European ancestry.

How Screening Test Works

A small amount of blood is collected from each baby born in North Carolina and sent to the state lab to test for various genetic diseases, including CF. The CF screening test looks for high levels of a protein known as IRT (immunoreactive trypsinogen) in the blood sample.

Trypsinogen (IRT) is a protein normally made in the pancreas. In people without CF, it is usually secreted into the intestines and does not reach high levels in the bloodstream. High levels of IRT might mean a child will have CF, but additional testing is needed to confirm the diagnosis.

One of these additional tests is run on the same blood sample at the state lab: a genetic (DNA) test for common mutations in the CF gene. If this second test detects two abnormal copies of the CF gene, the chance of that child developing CF is high.

Because there are so many possible mutations in the CF gene, not every mutation is detected in this second level of testing. Children with a screening test that finds one abnormal CF gene may have a second abnormal CF gene with a mutation that is not found by the screening test.

If the screening test shows high levels of IRT, that child should be evaluated at a specialized CF care center like Duke. Duke is one of five CF care centers in North Carolina that is accredited by the Cystic Fibrosis Foundation.

At the CF care center, the baby’s sweat will be tested to see if it has higher salt levels. If the sweat chloride (one part of salt) is high, the diagnosis of CF can be confirmed and the child can get any specialized care needed for babies with CF.

How Does CF Screening Help Children?

One of the main benefits of newborn screening for CF is being able to diagnose a child with CF earlier in life. This can help patients and families treat the problems of CF before a child develops severe symptoms.

Before newborn screening, CF was often diagnosed when children were several months or years old and showed up with complications from CF: frequent lung or sinus infections, malnutrition, intestinal blockage, or dehydration and electrolyte problems from losing too much salt in their sweat.

By working with a care team at a CF center like Duke, babies with CF can be started on any needed treatments before they develop significant complications of CF. Starting needed treatments early can prevent malnutrition, promote good lung health, and give children with CF their best chance at a long and fruitful life.

Further information regarding CF Newborn Screening is available on the CF Foundation Web site.

-- Christopher N. Fortner, MD, PhD, is a physician in Duke Children's Division of Pulmonary and specializes in all pediatric respiratory disorders, with special interest in diseases of the airways such as asthma or cystic fibrosis.

-- Dennis Clements, MD, PhD, MPH, is the chief of primary care pediatrics at Duke Children's Hospital.