Cystic Fibrosis (CF) Gene Mutations Testing

Send Us Your Feedback
  • Also Known As:
  • Cystic Fibrosis Genotyping
  • CF DNA Analysis
  • CF Gene Mutation Panel
  • CF Molecular Genetic Testing
  • Cystic Fibrosis Transmembrane Conductance Regulator Mutation Analysis
  • CFTR Mutation Analysis
  • Formal Name:
  • Cystic Fibrosis Gene Mutation Panel
Medically Reviewed by Expert Board

This page was fact checked by our expert Medical Review Board for accuracy and objectivity. Read more about our editorial policy and review process.

.
This article was last modified on
Learn more about...
Sweat Chloride Test

At a Glance

Why Get Tested?

To detect cystic fibrosis (CF) gene mutations; to screen for or help diagnose CF; to determine whether you are a carrier of a CF genetic mutation and to evaluate the risk of having a baby with CF

When To Get Tested?

When screening newborns for CF (all U.S. states screen for CF and some states use this test for screening); when an older child or adult has signs and symptoms of CF or a positive CF screening test; when someone wants to know their carrier status, such as a woman who is pregnant or considering pregnancy for the first time

Sample Required?

A blood sample drawn from an infant’s heel by collecting a spot of blood onto filter paper; for older children or adults, a blood sample obtained by inserting a needle into a vein in the arm; sometimes a scraping of the inner cheek (buccal swab) or, for prenatal testing, amniotic fluid obtained through amniocentesis or a chorionic villus sample

Test Preparation Needed?

None

Looking For Test Results?

Looking For Reference Ranges?

You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Testing.com. You may have been directed here by your lab’s website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab’s website or portal, or contact your healthcare practitioner in order to obtain your test results.

Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Cystic fibrosis (CF) is an inherited disease that affects mainly the lungs, pancreas, and sweat glands. It leads to the production of thick, sticky mucus and can cause recurrent respiratory infections and impaired function of the pancreas. The CF gene mutation panel detects the common mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene on chromosome 7 to screen for or diagnose CF or to identify carriers of the disease.

Each cell in the human body (except sperm and eggs) has 46 chromosomes (23 inherited from the mother and 23 from the father). Genes on these chromosomes form the body’s blueprint for producing proteins that control body functions.

Cystic fibrosis is caused by a mutation in each of the two copies of the CFTR gene (one copy from each parent). Both copies (alleles) of this gene pair must be abnormal to cause CF. If only one copy is mutated, the individual is a CF carrier. Carriers do not generally have any CF symptoms, but they can pass their abnormal CF gene copy on to their children.

To date, more than 2,000 different mutations of the CFTR gene have been identified, but only a few of the mutations are common. The majority of cystic fibrosis cases in the U.S. are caused by a mutation called deltaF508 (F508).

Recommendations by the American College of Medical Genetics (ACMG) and the American College of Obstetricians and Gynecologists (ACOG) have led to the adoption of a standard CF gene mutation panel. It includes 23 of the most common mutations (those with frequencies greater than 0.1% in the general U.S. population).

Some laboratories use expanded panels of up to 100 or more mutations designed to detect rare mutations particular to specific ethnic populations. These may provide slightly better sensitivity to detect mutations in some ethnic populations but are not recommended by ACOG for general screening. Some rare mutations are seen in only a few individuals and may not be detected with routine testing, even with an expanded panel.

In a CF gene mutation panel, the laboratory specifically examines the CFTR gene on each chromosome 7 for the 23 mutations. If the initial panel of mutations demonstrates a single mutation, additional testing for other less common mutations may be indicated if the individual is suspected of having CF.

How is the sample collected for testing?

A blood sample is drawn from an infant’s heel by collecting a spot of blood onto filter paper; for older children and adults, a blood sample is obtained by inserting a needle into a vein in the arm. A scraping of the inner cheek, called a buccal swab sample, may be collected. For prenatal testing, a sample of amniotic fluid may be collected using amniocentesis or a chorionic villus sample may be collected.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

 

Common Questions

How is it used?

Cystic fibrosis (CF) gene mutation testing may be used to screen for CF in newborns in some states (all U.S. states screen for CF and some states use this test for screening), to help diagnose CF, or to determine whether an individual is a carrier of a CF genetic mutation.

CF gene mutation testing may be used to follow up a positive initial test, such as an elevated immunoreactive trypsinogen (IRT) or positive sweat chloride test, to confirm the diagnosis of cystic fibrosis.

The CF mutation panel can be used as part of prenatal testing to determine whether prospective parents are carriers of a CF gene mutation and therefore at risk of passing the gene mutation to future children.

The American College of Obstetricians and Gynecologists recommends that carrier screening be made available to all women of reproductive age to identify couples at risk of having a child with CF. This is typically done by sequential testing:

  • In a sequential strategy, the mother is usually tested first. If she is not a carrier, then any child she had would, at most, be a carrier from the father’s side. Using this logic, the father is not tested.
  • A positive result for the mother should include the recommendation of testing her partner and at-risk family members.

All individuals with positive results for diagnostic tests or partners who are both identified as carriers should receive genetic counseling. In addition, any individuals who have a family history of CF should be referred for genetic counseling.

CF gene mutation testing can also be used for prenatal diagnosis if both parents are known to be carriers. DNA from amniocentesis and chorionic villus sampling procedures, although somewhat invasive, can be used to test the fetus for the mutations that have been identified in the parents.

When is it ordered?

A CF gene mutation panel may be ordered:

  • When you or your partner are planning to become pregnant
  • During the first trimester of pregnancy or the first prenatal visit
  • When someone has a close relative who has been diagnosed with cystic fibrosis
  • For an infant, soon after birth
  • When a person has had a positive CF screening test such as a sweat chloride conductivity test or IRT test
  • When a person has signs and symptoms of CF, such as:
    • Very salty sweat
    • Frequent respiratory infections, such as bronchitis or pneumonia
    • Wheezing, shortness of breath
    • Persistent diarrhea and/or foul-smelling, bulky, greasy stools
    • Delayed growth or poor weight gain (failure to thrive)
    • Vitamin deficiency, malnutrition
    • Infertility in men

What does the test result mean?

CF gene mutation testing results must be interpreted in the context of the person’s signs and symptoms and physical examination as well as medical and family history, ethnic background, and results of other laboratory tests.

If a CF gene mutation panel identifies two copies of gene mutations, then the person is diagnosed with cystic fibrosis. The test, however, cannot predict how severe or mild the symptoms may be. People with the exact same mutations may have very different outcomes.

If the CF gene mutation panel reveals a single copy of a mutation or is negative and the person tested has signs and symptoms of CF, then further mutation testing, a sweat chloride test, and/or other laboratory testing to evaluate organ function are warranted. The person may have a more rare form of CF that has not been identified or may have a lung or pancreatic disease or condition other than cystic fibrosis. The person may also be a carrier since some CF carriers may experience signs and symptoms related to CF.

If the CF gene mutation panel is positive for a single copy of a mutation and the person tested does not have signs and symptoms, then it is likely that the person is a CF carrier. If someone is identified as a carrier, then the siblings of this person may also want to verify their carrier status.

If the panel results are negative for mutations and the person has no signs or symptoms, then it is likely that the person does not have CF and is not a carrier. There is still a slight risk that someone who tests negative could be a carrier of a rare mutation not identified with the standard panel.

Is there anything else I should know?

Early diagnosis of cystic fibrosis allows those affected to be referred to CF centers for specialized care, individualized treatment plans, and careful monitoring. Beginning treatments such as taking oral enzyme supplements and fat-soluble vitamins, learning how to clear mucus out of airways, and learning to recognize respiratory infections can improve a person’s quality of life and minimize CF complications.

Healthcare practitioners may have varying approaches to screening and diagnosing CF, and gene mutation testing may involve a series of steps. Sometimes, a healthcare practitioner will choose to order a standard panel that includes 23 of the most common mutations. If results are negative and the clinical suspicion is still high that a person has CF, the healthcare practitioner may then request that an expanded panel be performed, or a negative result may automatically generate (reflex) a request for an expanded panel.

Based on the ancestry of the individual tested, some healthcare practitioners may immediately start with the expanded panel. In either scenario, a negative screening panel result may lead to a request for gene sequencing, a method that can identify rare mutations not detected by the standard or expanded panel.

Will this CF gene mutation panel detect any other genetic diseases?

No, it is only checking for specific CF mutations. Currently, every genetic disease requires specific DNA testing to identify it (assuming that the gene and mutations causing it are known).

Does this test detect all genetic causes of cystic fibrosis?

No. To date, more than 2,000 different mutations of the CFTR gene that cause cystic fibrosis have been identified, but only a few of the mutations are common. Some laboratories use the standard panel recommended by the American College of Medical Genetics and the American College of Obstetricians and Gynecologists that tests for 23 of the most common mutations (those with frequencies greater than 0.1% in the general U.S. population). Some laboratories offer expanded panels of up to 100 or more mutations. However, even these will not detect all genetic causes of cystic fibrosis.

Does my risk of being a carrier vary depending on my ethnic background?

Yes. Generally, the frequency of CF carriers is highest in Caucasians and Ashkenazi Jewish populations and is lower in other ethnic groups. According to the American College of Obstetricians and Gynecologists, the risk of being a carrier before genetic testing for different ethnic groups are estimated as follows:

  • Caucasians: 1 in 25
  • Ashkenazi Jewish: 1 in 24
  • Hispanic white: 1 in 58
  • African American: 1 in 61
  • Asian American: 1 in 94

Since the ancestry of the U.S. population is becoming increasingly blended, the historical data and statistical risks are changing. Quoted risks based on ancestry are estimates, and the risk for individuals of mixed ancestry may be unknown. Some families may also carry the additional risk of specific rare mutations within their family tree.

Do all states require or offer newborn screening for CF? Do I need to request it?

Every state’s newborn screening program includes a test for cystic fibrosis, so you will not need to request it. The method used may vary, with some states performing a blood test to determine the level of immunoreactive trypsinogen (IRT) and others screening for CF with gene mutation testing.

Related Content

On This Site

Tests: Sweat Test, Immunoreactive Trypsinogen

Conditions: Cystic Fibrosis, Lung Diseases, Pancreatic Diseases
Screening: Pregnancy: First Trimester, Newborns: Congenital and Genetic Disorders

Elsewhere On The Web

The National Institute of Diabetes and Digestive and Kidney Diseases: Cystic Fibrosis Research
ACOG: Cystic Fibrosis: Prenatal Screening and Diagnosis
National Newborn Screening & Global Resource Center: Newborn Screening
Cystic Fibrosis Foundation
Boomer Esiason Foundation: Fighting Cystic Fibrosis
National Society of Genetic Counselors

 

View Sources

Sources Used in Current Review

(© 2016). Diagnosing and Treating Cystic Fibrosis. American Lung Association. Available online at http://www.lung.org/lung-health-and-diseases/lung-disease-lookup/cystic-fibrosis/diagnosing-and-treating-cf.html. Accessed on 11/12/16.

Lyon, E. et. Al (2016 October Updated). Cystic Fibrosis – CF. ARUP Consult. Available online at https://arupconsult.com/content/cystic-fibrosis. Accessed on 11/12/16.

Sharma, G. (2016 June 8 Updated). Cystic Fibrosis. Medscape Drugs and Diseases. Available online at http://emedicine.medscape.com/article/1001602-overview Accessed on 11/12/16.

(© 2106).Diagnosis: Testing: CFTR Mutation Analysis. John Hopkins Cystic Fibrosis Center. Available online at http://www.hopkinscf.org/what-is-cf/diagnosis/testing/cftr-mutation-analysis/ Accessed on 11/12/16.

(© 1995–2016). Cystic Fibrosis Mutation Analysis, 106-Mutation Panel. Mayo Clinic Mayo Medical Laboratories. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/35386. Accessed on 11/12/16.

(2011 April, 2014 Reaffirmed). Update on Carrier Screening for Cystic Fibrosis. The American College of Obstetricians and Gynecologists. Available online at http://www.acog.org/Resources-And-Publications/Committee-Opinions/Committee-on-Genetics/Update-on-Carrier-Screening-for-Cystic-Fibrosis. Accessed on 11/12/16.

(2016 February). Cystic Fibrosis: Prenatal Screening and Diagnosis. The American College of Obstetricians and Gynecologists. Available online at http://www.acog.org/Patients/FAQs/Cystic-Fibrosis-Prenatal-Screening-and-Diagnosis. Accessed on 11/12/16.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber’s Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

NIDDK (July 1997). Cystic Fibrosis Research Directions. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) [NIH Publication No. 97-4200]. Available online at http://www.niddk.nih.gov/health/endo/pubs/cystic/cystic.htm.

Cystic Fibrosis Foundation. Sweat Testing Procedure and Commonly Asked Questions. [On-line information]. Available online at http://www.cff.org/publications01.htm.

Tait, J., et. al. (26 March 2001). Cystic Fibrosis. GENEReviews [On-line information]. Available online at http://www.genetests.org/.

Mayo Clinic (2001, February 09). What is Cystic Fibrosis? Mayo Clinic [On-line information]. Available online at http://www.mayoclinic.com/invoke.cfm?objectid=2CEBF76F-D36A-4D15-B937BFF91AB51438.

MedinePlus (2002, January 2, Updated). Cystic Fibrosis. MedlinePlus Health Information [On-line Information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000107.htm.

MedlinePlus (2002, January 2, Updated). Sweat Electrolytes. MedlinePlus Health Information [On-line Information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003630.htm.

MedlinePlus (2002, January 2, Updated). Trypsin and chymotrypsin in stool. MedlinePlus Health Information [On-line Information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003594.htm.

Mountain States Genetics (1999, September, Revised). Cystic Fibrosis (CF). Newborn Screening Practitioner’s Manual [On-line information]. Available online at http://www.mostgene.org/pract/prac26.htm.

National Institutes of Health (1995, November). Facts About Cystic Fibrosis. National Heart, Lung, and Blood Institute NIH Publication No. 95-3650 [On-line information]. Available online at http://www.nhlbi.nih.gov/health/public/lung/other/cf.htm.

Quest Diagnostics NEWS (2002, Winter). What is the Best Test to Screen for Cystic Fibrosis? [On-line serial]. PDF available for download at http://www.questdiagnostics.com/hcp/files/02winter_newsletter.pdf through http://www.questdiagnostics.com.

MedlinePlus (2002, January 2, Updated). Neonatal cystic fibrosis screening. MedlinePlus Health Information [On-line Information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003409.htm.

Drkoop (2001). Cystic fibrosis. Medical Encyclopedia [On-line information]. Available online at http://www.drkoop.com/conditions/ency/article/000107.htm.

MedlinePlus (2002, January 2, Updated). Trypsinogen. MedlinePlus Health Information [On-line Information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003560.htm.

Biomedical Hypertext (1999 May 20, last update). Exocrine Secretions of the Pancreas. Colorado State University [On-line information]. Available online at http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/pancreas/exocrine.html.

UPCMD (1998 – 2002). Cystic Fibrosis. University Pathology Consortium, LLC [On-line information]. Available online at http://www.upcmd.com/dot/examples/00218/description.html.

Sainato, D., (2002, March). Genetic Testing for CF Going Mainstream? Clinical Laboratory News [Journal], Vol 28.

Peter Jacky, PhD, FACMG. Director of Cytogenetics and Molecular Genetics, Airport Way Regional Laboratory, Portland, OR.

(Update April 23, 2008) National Newborn Screening and Genetics Resources Center. National Newborn Screening Status Report. Available online at http://genes-r-us.uthscsa.edu/nbsdisorders.htm. Accessed January 2009.

American College of Obstetricians and Gynecology (ACOG). Cystic fibrosis Carrier Testing: The Decision is Yours. Available online at http://www.acog.org/from_home/wellness/cf001.htm. Accessed January 2009.

(February 19, 2008) American Medical Association. Cystic fibrosis testing (including recommendations by ACMG and ACOG). Available online at http://www.ama-assn.org/ama/pub/category/9181.html. Accessed January 2009.

Human Genome Project Information. Genetic Disease Profile: Cystic Fibrosis. Available online at http://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/cf.shtml. Accessed January 2009.

(November 17 2008) MedlinePlus Medical Encyclopedia. Cystic Fibrosis. Available online at http://www.nlm.nih.gov/medlineplus/cysticfibrosis.html. Accessed January 2009.

(July 2008) National Heart, Lung, Blood Institute. Cystic Fibrosis, How Is Cystic Fibrosis Diagnosed? Available online at http://www.nhlbi.nih.gov/health/dci/Diseases/cf/cf_diagnosis.html. Accessed January 2009.

Denise I. Quigley, PhD, FACMG. Co-Director Cytogenetics/Molecular Genetics, Airport Way Regional Laboratory, Portland, OR.

Peter Jacky, PhD, FACMG. Director of Cytogenetics and Molecular Genetics, Airport Way Regional Laboratory, Portland, OR.

(Updated 2011 September 27) Learning about Cystic Fibrosis. National Human Genome Research Institute [On-line information]. Available online at http://www.genome.gov/10001213. Accessed August 2012.

(© 1995-2012). Cystic Fibrosis Mutation Analysis, 106-Mutation Panel. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/9497. Accessed September 2012.

Sharma, G. (2012 May 15). Cystic Fibrosis. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/1001602-overview. Accessed August 2012.

Ooi, C. et. al. (2012 July 27). Comparing the American and European Diagnostic Guidelines for Cystic Fibrosis Same Disease, Different Language? Medscape Today News from Thorax. v67 (7):618-624. [On-line information]. Available online at http://www.medscape.com/viewarticle/766511. Accessed September 2012.

Bender, L. et. al. (2011 September 29). Kids in America Newborn Screening for Cystic Fibrosis. Medscape Today News from Lab Med v42 (10):595-601 [On-line information]. Available online at http://www.medscape.com/viewarticle/750133. Accessed September 2012.

Grenache, D. et. al. (Updated 2012 April) Cystic Fibrosis – CF. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/CF.html?client_ID=LTD#tabs=0. Accessed September 2012.

Cystic Fibrosis Foundation. Cystic Fibrosis Newborn Screening. Available online at http://www.cff.org/AboutCF/Testing/NewbornScreening/ScreeningforCF/. Accessed May 2012.

American College of Medical Genetics. Technical Standards and Guidelines for CFTR Mutation Testing, 2006 Edition.

Timothy S. Uphoff, Ph.D., D(ABMG), MLS(ASCP)CM. Section Head Molecular Pathology Laboratory, Marshfield Labs, Marshfield Clinic, Marshfield WI.

 

Ask a Laboratory Scientist

Ask a Laboratory Scientist

This form enables patients to ask specific questions about lab tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. Please allow 2-3 business days for an email response from one of the volunteers on the Consumer Information Response Team.

Send Us Your Question