Information for Health Professionals
Carrier screening for recessive disorders has typically
targeted disorders prevalent in specific ethnic groups: for example,
Tay-Sachs disease in Ashkenazi Jews, cystic fibrosis in Caucasians, sickle
cell anemia in African-Americans, and beta-thalassemia in persons of Mediterranean
ancestry. New techniques make it feasible to offer carrier screening
for a large number of recessive conditions that affect persons of many
different ethnicities .
does enhanced carrier screening work?
DNA from a
blood or saliva sample is analyzed for hundreds of different mutations,
each of which is associated with a particular disease. For some conditions,
a single mutation is assessed, whereas for others, more than a dozen mutations
are analyzed. Carriers of a particular disorder are identified when
one copy of a mutation for that disease is detected.
are the benefits of enhanced carrier screening?
isn't there a downside to expanded screening?
A single small
sample can be tested for cystic fibrosis, fragile X, and spinal muscular
atrophy carrier status, in addition to dozens of other, rarer, autosomal
Ashkenazi Jewish ancestry can be tested, economically, for over a dozen
For persons of
various ethnic minorities, carrier status can be determined for disorders
prevalent in their communities.
Quite frankly, there is. When screening
for such a large number of rare diseases, many people will be identified
as carriers for one, and sometimes two or three diseases. Usually,
their reproductive partner will screen negative for the same disease(s).
However, in some cases, there will still be a significant "residual risk"
for having an affected child, because carrier screening may be considerably
less than 100% sensitive. More sensitive methods of carrier screening
for individual diseases are available, but they are often quite expensive.
points to keep in mind:
for pan-ethnic carrier screening?
is available when both parents are identified as carriers for an autosomal
recessive disorder, and when a woman is found to be a fragile X carrier.
The cost of enhanced
carrier screening may be higher than routine, more limited screening.
However, in some cases, such as for couples of Ashkenazi ancestry, pan-ethnic
screening can actually be considerably less expensive.
is most useful for couples who are of various ethnic minorities, when diseases
prevalent in those ethnic groups are included on a particular laboratory's
Reports for such
extensive testing tend to be very long, but most laboratories highlight
the abnormal results prominently on the first page.
Enhanced screening is a convenient and
economical option, particularly for patients who have not had prior carrier
screening, since it includes screening recommended for Caucasian couples
(cystic fibrosis) and carrier screening that some professional societies
have recommended (fragile X and spinal muscular atrophy), as well as the
extended disease panel. Each laboratory performing pan-ethnic screening
has slightly different disease and mutation panels. Genetic consultation
is helpful when one or both members of a couple have abnormal screening
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This page last updated on January 31,