Cystic Fibrosis Testing
What is Cystic Fibrosis?
CF begins in infancy or early childhood, and may include pneumonia, breathing
problems, lung damage, intestinal problems, and poor growth. While CF treatment
has improved, death may occur in early childhood or as a young adult. The
average lifespan is about 31 years. Cystic fibrosis (CF) is an inherited
disorder which occurs in about 1 in 2,500 live births. CF occurs more often in
Caucasian and Jewish individuals than in other ethnic groups.
How is CF Inherited?
CF is inherited as a recessive genetic disorder. Recessive means the effect
of the CF gene is only seen when a baby inherits a CF gene from both parents.
Parents of a CF baby carry one CF gene and one normal gene and are unaffected CF
carriers. When both parents carry a CF gene, they have a 1 in 4 (25%) chance of
having a baby with CF with each pregnancy; a 2 in 4 (50%) chance the baby will
carry the CF gene, but not have CF; and a 1 in 4 (25%) chance the baby will not
carry the gene.
Why Screen for CF?
Screening can identify CF carrier couples, who can then make informed
decisions about pregnancy options including having prenatal diagnosis. Both
partners can be tested at the same time to receive the most accurate estimate of
their risk of having a baby with CF.
Who Should be Offered CF Testing?
The chance a relative will inherit the CF gene depends on which relative has CF:
|
Affected relative |
Carrier Chance |
|
Brother or sister |
2 in 3 (67%) |
|
Niece or nephew |
1 in 2 (50%) |
|
Aunt or uncle |
1 in 3 (33%) |
|
First cousin |
1 in 4 (25%) |
CF carrier testing for relatives is most reliable if the CF genes are known for the CF relative.
|
Ethnic Group |
Carrier Chance |
Detection |
|
Caucasian (white) |
1 in 25 |
90% |
|
Jewish |
1 in 29 |
97% |
|
Hispanic American |
1 in 46 |
72% |
|
African American |
1 in 65 |
69% |
How is Testing Done?
You may discuss CF
testing with your healthcare provider and consider having genetic counseling.
The DNA blood test can identify carriers of the 33 most
common CF genes. This test will detect 90% of CF
carriers in Caucasians, 97% in Ashkenazi Jewish, 72% in Hispanic
Americans, and 69% in African Americans. If
the DNA carrier test does not detect a CF gene, the risk of being a carrier is
reduced, but not eliminated. Testing more CF genes will not significantly
improve the detection rate.
Time to Complete Tests:
Carrier and affected individuals’ tests are completed within 1 week and
prenatal tests will take about 2-3 weeks.
Specimen Transport:
SHIP AT ROOM TEMPERATURE in our kit to: GeneCare Medical Genetics Center 120 Conner Drive, Suite 201, Chapel Hill, NC 27514-7085
By DHL/Airborne (800) 247-2676 priority overnight or by our courier service to reach GeneCare Monday-Thursday. Delivery required within 24 hours. For Friday shipments, mark Saturday Priority Overnight delivery.
Notify GeneCare of shipment date and DHL/Airborne airbill tracking number.
Specimen Collection:
● Call GeneCare at 1-800-277-4363 to discuss clinical indications, current testing, informed consent, fees, and payment method.
● Complete Consent Forms and Laboratory Request. (See Special DNA tests) Enclose family history.
● Label each specimen tube with patient name, birth date, and collection date.
Specimen: Collect 10-15cc of blood in lavender top EDTA tube OR two buccal swabs (1 from each cheek).
Cystic Fibrosis Carrier Screening Policy:
In April, 1997, an independent scientific panel set up by The National
Institutes of Health recommended ..."Genetic testing for CF should be
offered to adults with a positive family history of CF, to partners of people
with CF, to couples currently planning a pregnancy, and to couples seeking
prenatal care." In 2001, the American College of Obstetricians and
Gynecologists and The American College of Medical Genetics issued similar
statements.
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