Karyotype Test

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Update Date 12/05/2020
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Know the basics

What is Karyotype Test?

Karyotype is a test to identify and evaluate the size, shape, and number of chromosomes in a sample of body cells. Extra or missing chromosomes, or abnormal positions of chromosome pieces, can cause problems with a person’s growth, development, and body functions.

Why is Karyotype Test performed?

This test may be done:

  • On a couple that has a history of miscarriage
  • To examine any child or baby who has unusual features or developmental delays

The bone marrow or blood test can be done to identify the Philadelphia chromosome, which is found in about 85% of people with chronic myelogenous leukemia (CML).

The amniotic fluid test is done to check a developing baby for chromosome problems.

Things to know before

What should I know before receiving Karyotype Test?

Since the sex chromosomes (XX or XY) are identified during the chromosome analysis, this test will also, as a byproduct, definitely determine the sex of a fetus.

Some chromosome alterations are too small or subtle to detect with karyotyping. Other testing technique such as fluorescent in situ hybridization (FISH) or a microarray may sometimes be performed to further investigate chromosomal abnormalities.

It is possible for people to have cells in their body with differing genetic material. This happens because of changes early in the development of a fetus that lead to the development of distinctly different cell lines and is called mosaicism. An example of this is some cases of Down syndrome. The affected person can have some cells with an extra third chromosome 21 and some cells with the normal pair.

Know what happens

How to prepare for Karyotype Test?

You do not need to do anything before you have 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.

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) condition 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.

What happens during Karyotype Test?

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.
  • Apply pressure to the site and then a bandage.

Cell sample from a fetus

For this type of test, cells are collected from the fetus using amniocentesis or chorionic villus sampling.

Cell sample from bone marrow

Bone marrow aspiration may be used for a karyotype test.

What happens after Karyotype Test?

An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

You may remove the tape and cotton in about 20 to 30 minutes. You will be dated to get the results of your test. Your doctor will explain what your test results mean for you. You should follow the instructions of your doctor.

Understand the results

What do my results mean?

Results of a karyotype test are usually available within 1 to 2 weeks.

Normal: There are 46 chromosomes that can be grouped as 22 matching pairs and 1 pair of sex chromosomes (XX for a female and XY for a male).

The size, shape, and structure are normal for each chromosome.

Abnormal: There are more than or fewer than 46 chromosomes.

The shape or size of one or more chromosomes is abnormal.

A chromosome pair may be broken or incorrectly separated.

Depending on the laboratory and hospital, the normal range for Karyotype test may vary. Please discuss with your doctor any questions you may have about your test results.

If you have any questions about the Karyotype test, please consult with your doctor to better understand your instructions.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Read also:


    Karyotype Test. http://www.webmd.com/baby/karyotype-test?print=true. Accessed July 4, 2016.
    Karyotyping. https://www.nlm.nih.gov/medlineplus/ency/article/003935.htm. Accessed July 4, 2016.
    Chromosome Analysis (Karyotyping). https://labtestsonline.org/understanding/analytes/chromosome-analysis/tab/test/. Accessed July 4, 2016.

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