At a Glance
Why Get Tested?
When to Get Tested?
As part of routine care when a woman is pregnant or considering pregnancy for the first time; when someone wants to know their carrier status; when screening newborns for CF in some states; when someone has signs and symptoms of CF
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 prenatal (amniocentesis or chorionic villus) specimens
Test Preparation Needed?
The Test Sample
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 mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene on chromosome seven to identify carriers of the disease and to screen for or help make a diagnosis of CF.
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. They are not ill, but they can pass their abnormal CF gene copy on to their children.
To date, more than 1,500 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 pick up 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 seven 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 the disease.
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, or prenatal (amniocentesis or chorionic villus) specimens may also be used.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
(Updated 2011 September 27) Learning about Cystic Fibrosis. National Human Genome Research Institute [On-line information]. Available online at http://www.genome.gov/10001213 through http://www.genome.gov. 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 through http://www.mayomedicallaboratories.com. 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 through http://emedicine.medscape.com. 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 through http://www.medscape.com. 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 through http://www.medscape.com. 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 through http://www.arupconsult.com. Accessed September 2012.
Cystic Fibrosis Foundation. Cystic Fibrosis Newborn Screening. Available online at http://www.cff.org/AboutCF/Testing/NewbornScreening/ScreeningforCF/ through http://www.cff.org. 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.
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 through http://www.niddk.nih.gov.
Cystic Fibrosis Foundation. Sweat Testing Procedure and Commonly Asked Questions. [On-line information]. Available online at http://www.cff.org/publications01.htm through http://www.cff.org.
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 through http://www.mayoclinic.com.
MEDLINEplus (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 through http://www.mostgene.org.
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 through http://www.nhlbi.nih.gov.
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 through http://www.drkoop.com.
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 through http://arbl.cvmbs.colostate.edu.
UPCMD (1998 – 2002). Cystic Fibrosis. University Pathology Consortium, LLC [On-line information]. Available online at http://www.upcmd.com/dot/examples/00218/description.html through http://www.upcmd.com.
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 through http://genes-r-us.uthscsa.edu. 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 through http://www.acog.org. 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 through http://www.ama-assn.org. 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 through http://www.ornl.gov. 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 through http://www.nhlbi.nih.gov. 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.