Cystic Fibrosis Screening Tests
Cystic fibrosis (CF) is a genetic
disorder that causes digestive and breathing problems. It causes the
body to produce sticky mucus that builds up in the lungs, pancreas and
other organs, which can lead to respiratory and digestive problems.
Those with the disorder are usually diagnosed early in life.
We are now able to determine whether
there is a risk of having a baby with CF. You and your partner can be
tested before pregnancy to determine if either of you are carriers. A
test can also be done in the first and/or second trimester of pregnancy
to see if the baby has cystic fibrosis.
For your baby to have cystic fibrosis, both parents must be carriers. If only one parent is a carrier, the baby will not have CF. A carrier does not
have CF. You could be a carrier even if no one in your family has CF.
You could also be a carrier if you already have children and they do
not have CF. Your chance of carrying the gene for cystic fibrosis
increases if someone in your family has CF or is a known carrier.
Screening for cystic fibrosis is often part of genetic counseling. One test available is called Cystic Fibrosis (CF) Complete Test. It can identify more than 1000 mutations of the CF gene. A panel that screens for 23 CF mutations is the recommended test.
If you and your partner are Caucasian,
the American College of Obstetricians and Gynecologist (ACOG)
recommends CF screening. Cystic fibrosis is the most common birth
defect in this group. Screening is also recommended for those at higher
risk for CF, such as Ashkenazi Jews. The screening test uses a blood
sample or a saliva sample.
If both you and your partner carry the CF
gene, your baby has a 25% chance of having cystic fibrosis. Your
developing baby can be tested for CF during your pregnancy with
chorionic villus sampling around week 10 or 11 of pregnancy.
Amniocentesis may also be used to test the baby.
Some CF gene mutations cannot be detected
by the current test; you could be told you don’t carry the gene when in
fact you do. The test cannot detect all CF mutations because
researchers don’t know all of them at this time. However, unknown CF
gene mutations are rare.
If you believe cystic fibrosis is a
serious concern or if you have a family history of the disease, talk to
your healthcare provider. Testing is a personal decision you and your
partner must make.
Many
couples choose not to have the test because it would not change what
they would do during the pregnancy. In addition, they do not want to
expose the mother-to-be or the developing fetus to the risks of CVS or
amniocentesis. However, testing is recommended so care can be provided
to baby immediately after birth if he or she has CF.
Jewish Genetic Disorders
A group of medical conditions
considered genetic disorders occur more commonly among Ashkenazi Jews,
who are of eastern European descent. About 95% of the Jewish population
in North America is of Ashkenazi heritage. Some of the diseases found
in this group also affect Sephardi Jews and non-Jews; however, the
conditions are more common among Ashkenazi Jews—sometimes 20 to 100
times more common.
Much research has been done to determine
why these disorders occur more frequently in the Ashkenazi Jewish
population. Researchers believe two processes are at work—the founder
effect and genetic drift.
With the founder effect, genes
that cause certain problems just happened to occur among the founders
of the Ashkenazi Jews. They emigrated to eastern Europe around 70 A.D.
Before they left Palestine, these disorders were probably as common
among all other groups in the area. When the Ashkenazi Jews settled
together in Europe, they carried these genes.
Because Ashkenazi Jews do not often marry
outside their faith or community, the genes were not spread among other
communities. This is called genetic drift. The presence of the
genes was not decreased by introducing genes from outside the
community, so many of the problems remained within this group.
Some diseases and conditions occur within
other Jewish groups, such as Sephardi Jews. Sephardi Jews are of
Spanish or Portuguese descent, and particular disorders occur within
this group, probably for the same reasons they occur among Ashkenazi
Jews.
Various conditions are considered “Jewish
genetic disorders.” However, we know people of other ethnic backgrounds
can inherit some of these diseases. Some diseases and conditions are
not usually found outside the various Jewish populations and are rare
in the general population. These disorders include:
•Tay-Sachs disease
•Bloom syndrome
•factor-XI deficiency
•familial dysautonomia (Riley-Day syndrome)
•Fanconi anemia (Group C)
•Gaucher disease
•glucose-6 phosphate dehydrogenase deficiency (G6PD)
•glycogen storage disease, type III
•mucolipidosis IV
•Niemann-Pick disease (Type A)
•nonclassical adrenal hyperplasia
•nonsyndromic hearing loss
•torsion dystonia
Screening tests are available for some of
the diseases listed above. One test targets 11 genetic diseases and is
designed for couples in which one or both members are of Ashkenazi or
Sephardi Jewish descent. Many diseases can be identified before
pregnancy or in early pregnancy. Discuss testing with your healthcare
provider if you’re interested.
