Karyotype is a test to identify and evaluate
the size, shape, and number of
chromosomes in a sample of body cells. Extra, missing,
or abnormal positions of chromosome pieces can cause problems with a person's
growth, development, and body functions.
Determine whether the chromosomes of an adult
have an abnormality that can be passed on to a child.
Determine
whether a chromosome defect is preventing a woman from becoming pregnant or
causing
miscarriages.
Determine whether a
chromosome defect is present in a
fetus. Karyotyping also may be done to determine
whether chromosomal problems may have caused a fetus to be
stillborn.
Determine the cause of a baby's birth defects or
disability.
Help determine the appropriate treatment for some types
of cancer.
Identify the sex of a person by determining the presence
of the Y chromosome. This may be done when a newborn's sex is not clear.
No special preparation is needed before
having this test.
Talk to your doctor about any concerns you have
about the need for the test, its risks, or how it will be done. To help you
understand the importance of this test, fill out the
medical test information form(What is a PDF document?).
Since the information obtained from
karyotyping can have a profound impact on your life, you may want to see a
doctor who specializes in genetics (geneticist) or a
genetic counselor. This type of counselor is trained
to help you understand what karyotype test results mean for you, such as your
risk for having a child with an inherited (genetic) disease like
Down syndrome. A genetic counselor can help you make
well-informed decisions. Ask to have
genetic counseling before making a decision about a
karyotype test.
Karyotype testing can be done using
almost any cell or tissue from the body. A karyotype test usually is done on a
blood sample taken from a vein. For testing during pregnancy, it may also be
done on a sample of
amniotic fluid or the
placenta.
Blood sample from a vein
The health professional
drawing your blood will:
Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
Clean the needle site with
alcohol.
Put the needle into the vein. More than one needle stick
may be needed.
Attach a tube to the needle to fill it with
blood.
Remove the band from your arm when enough blood is
collected.
Apply a gauze pad or cotton ball over the needle site as
the needle is removed.
You may feel nothing at
all from the needle puncture, or you may feel a brief sting or pinch as the
needle goes through the skin. Some people feel a stinging pain while the needle
is in the vein. But many people do not feel any pain, or have only minor
discomfort, once the needle is positioned in the vein. The amount of pain you
feel depends on the skill of the health professional drawing the blood, the
condition of your veins, and your sensitivity to pain.
There is very little risk
of complications from having blood drawn from a vein.
You may develop a small bruise at the
puncture site. You can reduce the risk of bruising by keeping pressure on the
site for several minutes after the needle is withdrawn.
In rare
cases, the vein may become inflamed after the blood sample is taken. This
condition is called phlebitis and is usually treated with a warm compress
applied several times daily.
Continued bleeding can be a problem
for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other
blood-thinning medicines can also make bleeding more likely. If you have
bleeding or clotting problems, or if you take blood-thinning medicine, tell
your health professional before your blood is drawn.
Reasons you may not be able to
have the test or why the results may not be helpful include:
Being treated for cancer. Chromosomes may be
damaged by some types of cancer treatment.
The area where the cells
are collected. The results of a karyotype test may depend on whether the cells
were collected from the amniotic fluid, the fetus, or the placenta.
Your doctor will discuss with you any factors that can
interfere with your test and the accuracy of the results.
Sometimes a karyotype test is combined with
other genetic tests to provide more specific information about genetic
problems. For more information, see the medical test
Genetic Test.
If the results of karyotype
are abnormal, other family members may be advised to undergo testing.
A sample taken by gently swabbing the tissues inside the cheek
(called a buccal swab) sometimes is used for a karyotype test. But results from
buccal swabbing are less accurate than other types of karyotype
tests.
Since the information obtained from karyotyping can have a
profound impact on your life, you may want to see a doctor who specializes in
genetics (geneticist) or a
genetic counselor. This type of counselor is trained
to help you understand what karyotype test results mean for you, such as your
risk for having a child with a disease like
Down syndrome that is caused by a chromosome problem.
A genetic counselor can help you make well-informed decisions. Ask to have
genetic counseling before making a decision about a
karyotype test.
This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.
