Cystic Fibrosis Gene Test

By Dr. Brandon Colby MD, an expert in genetic testing and personalized medicine.

Cystic Fibrosis (CF) is a serious genetic disorder affecting approximately 70,000 people worldwide. One in every 3,200 babies are born with CF, making it one of the most common inherited genetic disorders among people of Caucasian descent.

The American College of Obstetricians and Gynecologists (ACOG) and the American College of Medical Genetics (ACMG) recommend that all Caucasian couples who are pregnant or considering pregnancy check to see if they are cystic fibrosis carriers. They also encourage people of other ethnicities to consider screening, with the understanding that detection rates vary across populations.

About Carrier Screening for Cystic Fibrosis

Genetic testing for cystic fibrosis can identify whether someone is a CF carrier. Many people pursue the cystic fibrosis gene test due to a family history of the disease, but carrier screening is a good idea for everyone. This is especially relevant for pregnant individuals, as prenatal screening helps parents learn about the disease and plan for any healthcare needs.

Carrier testing can identify whether you carry a faulty cystic fibrosis transmembrane conductance regulator (CFTR) gene. This gene is responsible for causing CF. The Cystic Fibrosis Foundation reports that more than 10 million Americans carry one mutation of the CFTR gene. The delta F508 mutation is the most common and accounts for approximately 70% of all mutations found.

Who Should Get Genetic Testing for Cystic Fibrosis

While CF can affect people of all backgrounds, it is more prevalent among Caucasians. Ashkenazi Jewish descendants are at increased risk, with a carrier detection rate of up to 97% and approximately 1 in 3,000 people of this descent affected. Anyone with Ashkenazi Jewish ancestry should consider a gene test, particularly those with a known family history of CF.

Prenatal Testing for Cystic Fibrosis

Two cystic fibrosis gene tests available during pregnancy are amniocentesis and chorionic villus sampling (CVS).

• Amniocentesis tests cells from the amniotic fluid. It is performed between the 15th and 20th weeks of pregnancy.
• CVS checks cells from the placenta. This test is done during the 10th and 12th weeks of pregnancy.

Newborn Screening for Cystic Fibrosis

Babies are screened for cystic fibrosis before leaving the hospital as part of the standard newborn screen. Every newborn has a blood test taken from the heel to check the levels of immunoreactive trypsinogen (IRT), a chemical produced by the pancreas. This screen includes CF among many different conditions.

Other Times to Consider a Cystic Fibrosis Gene Test

• Symptoms such as frequent respiratory infections or very salty sweat may warrant a genetic test. A sweat test can determine whether sweat chloride is too high.
• Diagnostic testing is conducted when a healthcare provider suspects CF based on clinical presentation.
• When initial diagnostic tests come back positive, a cystic fibrosis gene test can confirm the diagnosis.
• When a close relative has been diagnosed with CF, family members may want to determine whether they are carriers.

What to Expect with a Cystic Fibrosis Gene Test

Genetic testing uses genetic material collected from cells. The material can come from blood, saliva, or tissue from inside the cheek. The sample goes to a laboratory for analysis. Depending on what was ordered, the test can check for CFTR mutations as well as other common mutations. Results will indicate any gene mutations found in the sample.

What the Results Mean

Receiving a "carrier status" result does not mean a child will have CF. It simply means the person carries one CF mutation. Because a child must inherit two copies of the faulty CF gene, one from each parent, it is important for both partners to be tested. If both partners are carriers, there is a higher probability that a child could inherit faulty CFTR genes from both sides.

A result showing two copies of the CF mutation means the person either has cystic fibrosis or may develop symptoms. In this case, follow-up with a genetic counselor or healthcare provider is strongly recommended.

How to Find Out if You Are a Carrier

You do not need to go through a healthcare provider to access genetic testing. With advancements in genomics, it is now possible to perform cystic fibrosis gene sequencing at home. Whole Genome Sequencing from Sequencing uses a simple cheek swab and can screen for CF gene mutations as well as over 15,000 additional conditions through the Next Gen Disease Screen.

Results from Whole Genome Sequencing are clinically accurate. Anyone who receives a positive result is encouraged to seek genetic counseling to fully understand the implications.

To order Whole Genome Sequencing, visit the Sequencing store.

Already have DNA data from another provider? Sequencing works with raw data files from virtually all testing companies including 23andMe, AncestryDNA, MyHeritage, FamilyTreeDNA, and many more. Upload your data for free and start exploring personalized insights across over 30,000 genes.

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