A karyotype test is recommended to monitor the number, shape, and size of chromosomes. Every person has a total 46 chromosomes, i.e. 23 pairs present in each cell. Amongst the 46 chromosomes, every individual inherits 23 chromosomes from their mother and the rest 23 from their father. A karyotype test is helpful to check if there is one or more missing or extra chromosome, or if all the chromosomes are normal in shape and size. Having abnormal numbers, shapes, and sizes of chromosomes are an indication of a specific genetic disorder. The test is also helpful to diagnose genetic defects in unborn babies.
Why is Karyotype Test Done?
- The test is recommended for a woman who has difficulty conceiving or has frequent miscarriages. Difficulty in conceiving or frequent miscarriages might also be because of chromosomal issues.
- The test is recommended in children to diagnose specific genetic disorders. If your family has a history of certain conditions, your doctor may recommend the test to check if the baby has inherited the condition.
- The test is recommended in pregnant women for their unborn baby to diagnose any congenital or birth defects. The test is only recommended if you have any risk factors that may make your baby develop any health condition.
- A karyotype test’s results are also helpful to suggest appropriate treatment options for cancer or any blood disorder. Your doctor may recommend karyotype testing if you have any signs and symptoms of leukaemia, lymphoma, or myeloma. The test is helpful to diagnose the condition as well to check the effectiveness of the treatment.
Prerequisites of a Karyotype Test
- Your doctor may help you with all the instructions you need to follow before the test.
- If you have any questions about the test, you may talk to your doctor and get it answered. Your doctor may even be referred to a genetic counselor to help you make any decision.
- You may also be required to sign a consent form before the test.
- It is a minimum risk test. The risks and complications involved in the test vary based on the method used to draw a sample for the test. If blood or bone marrow sample is drawn for the test, you may experience bleeding or bruising on the punctured area. If the amniotic fluid sample is drawn for the test, there may be some risk of miscarriage. Your doctor or lab technician will explain to you all the potential risks involved in the test.
Understanding the Results
The test results analyse the numbers, shapes, and sizes of chromosomes. It may take 10 to 15 days for the test results to come out.
Normal result
- Each chromosome is normal in shape, size, and structure.
- A normal test result indicates 46 chromosomes out of which two are considered sex hormones. The chromosomes are grouped in 22 matching pairs. 1 pair of sex chromosomes are two X chromosomes in females and one X and one Y chromosome in males.
Abnormal result
- The result may indicate abnormal if there are excess or less than 46 chromosomes.
- The result may also indicate abnormal if the shape or size of the chromosome is abnormal.
Having abnormal numbers of chromosomes may indicate certain health conditions such as Down’s syndrome, Edward’s syndrome, Triple XXX syndrome, Patau’s syndrome, or Turner’s syndrome.
Having an abnormal structure of chromosomes may indicate certain health conditions such as Prader Willi syndrome, Cat’s cry syndrome, duplication of chromosomal material, etc.
Your test result may also indicate ‘abnormal’ if you are undergoing cancer treatment as the chromosomes might be damaged during the treatment.
Consult your doctor to know the potential factors that may indicate abnormal result.
When should it be repeated?
Your doctor may ask you to repeat the test in the following conditions:
- If your previous test result indicates any abnormalities, you may need to repeat the test to confirm the diagnosis.
- In case your doctor suspects the previous test result as a false positive or false negative.
- If the sample collected for the test is not collected using the right technique.
- If the sample collected for the test is not enough.
- You may need to repeat the test if you are undergoing treatment for leukaemia, lymphoma, or myeloma. The test results are helpful to check the effectiveness of the treatment.
Procedure
The sample for the test can be collected from different tissues such as bone marrow, blood, amniotic fluid, and placenta. The procedure to collect sample varies based on the body part that is being tested.
- Blood sample – This procedure to collect blood sample is similar to any other blood test. The blood sample is collected from the vein of your arm and is stored in a tube. This blood sample is then sent to the lab for analysis. Collecting blood sample may take 5 to 10 minutes.
- Bone marrow – In this procedure, a sample of bone marrow is collected using a large bore needle and sent to the lab for analysis.
- Amniotic fluid – Amniotic fluid is the clear and yellowing fluid that surrounds the foetus inside the mother’s womb. In this procedure, a needle is inserted into the uterus via your abdomen and a sample of amniotic fluid is collected.
- Placenta – Placenta sample can be collected in two ways. The sample is either collected using a needle that is inserted into the placenta via your abdomen or by inserting a catheter via your vagina.
In newborn babies, the blood sample is collected through the heels.
Once the required sample is collected, it is sent to a laboratory that is well equipped with technology for karyotype analysis and has experts such as cytogenetic technologists.
Certain chemicals are added to the sample that helps to separate dividing and non-dividing cells.
Later, the dividing cells are grown using certain chemicals or hormones through cell culture process. Growing cells is a time-consuming process and may take a few days to complete this step.
Later certain chemicals are added to the cells and monitored under a microscope.
Learn more about screening tests for women here.
[embed-health-tool-ovulation]
