Karyotyping is a test to examine chromosomes in a sample of cells. This test can help identify genetic problems as the cause of a disorder or disease.
The test can be performed on almost any tissue, including:
To test amniotic fluid, an amniocentesis is done.
A bone marrow biopsy is needed to take a sample of bone marrow.
The sample is placed into a special dish or tube and allowed to grow in the laboratory. Cells are later taken from the new sample and stained. The laboratory specialist uses a microscope to examine the size, shape, and number of chromosomes in the cell sample. The stained sample is photographed to show the arrangement of the chromosomes. This is called a karyotype.
Certain problems can be identified through the number or arrangement of the chromosomes. Chromosomes contain thousands of genes that are stored in DNA, the basic genetic material.
Follow the health care provider's instructions on how to prepare for the test.
How the test will feel depends on whether the sample procedure is having blood drawn (venipuncture), amniocentesis, or bone marrow biopsy.
This test can:
This test may be done:
The bone marrow or blood test can be done to identify the Philadelphia chromosome, which is found in 85% of people with chronic myelogenous leukemia (CML).
The amniotic fluid test is done to check a developing baby for chromosome problems.
Your provider may order other tests that go together with a karyotype:
Normal results are:
Abnormal results may be due to a genetic syndrome or condition, such as:
Chemotherapy may cause chromosome breaks that affect normal karyotyping results.
Risks are related to the procedure used to obtain the sample.
In some cases, a problem may occur to the cells growing in the lab dish. Karyotype tests should be repeated to confirm that an abnormal chromosome problem is actually in the body of the person.
Reviewed By: Anna C. Edens Hurst, MD, MS, Assistant Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.