Karyotype Test | chromosome testing | Chromosome Analysis | Cytogenetic Analysis

A karyotype test is a whole chromosome analysis that looks at the shape, size, and number of chromosomes in a cell. A cell is the basic unit of life, containing a nucleus. Inside the nucleus contains chromosomes and the chromosome contains genes. DNA genetic material contains the genes which are passed down from the parents to the children. The external characteristics such as height and eye color etc., of humans, are determined by the information that the genes carry.

Another name for the karyotype is genetic testing, chromosome testing, Chromosome Analysis, or Cytogenetic Analysis.

Usually, most people have 46 total chromosomes in a cell and it is divided into 23 pairs. 22 pairs are called autosomes and two are sex chromosomes, X and Y. Each half of the chromosomes comes from the mother and father. But due to certain genetic conditions or abnormalities, some chromosomes are missed or have extra chromosomes or chromosomes can have an abnormal shape, size, or sequence (arrangement). 

What are the reasons to do the Karyotype test?

A karyotype test can be done for the below reasons :

1. In the case of male or female infertility where the couple is unable to get pregnant. Sometimes infertility is the result of a genetic disorder.
2. In case of cancer or blood disorders such as leukemia, anemia, lymphoma, or multiple myeloma may alter the chromosomes. Diagnosing these abnormalities through karyotype can be helpful in treatment guidance.
3. In the case of hereditary genetic conditions in the family. This test can predict if you have an abnormal chromosome and what is the probability of passing this genetic condition to your children.
4. A developing fetus or unborn baby in the womb may need a karyotype analysis test if the mother is at risk of a genetic disorder due to :

• • • • If the mother gets pregnant if she is above the age of 35 years.
      • Pregnant couples either the mother or father is having genetic disorders or a family history of a genetic condition.

The karyotype is also helpful in ruling out genetic disorders that have been the reason for death if a Miscarriage happens during the pregnancy or the baby dies after the birth.

After the birth also there may be the need for chromosome analysis if the baby is showing the sign of a genetic disorder. In this case, the baby can have many genetic disorders with many types of symptoms.

Read Here – General Information About Miscarriage: Symptoms, Causes, Risk Factors, Diagnostic Test, Types, Prevention, And Management

Who does the Karyotype test?

For the karyotype test, any trained technician can withdraw the blood or fluid samples depending on the requirement of the karyotype test. But the chromosome analysis is done by only the pathologist or geneticists who have undergone the training.

What preparation is required for this test?

No need for any special preparation for most people for a karyotype test. If you have recently received a blood transfusion then it becomes necessary to inform your doctor whether to wait for this test.

Also, ask your doctor if there is a requirement for fasting or if you should avoid any medication before this test.

This test brings a lot of impact on the life of people, especially in the case of parents who have discovered that their baby has a genetic disorder. They can take consultation with a certified genetic counselor before and after taking this test and should understand the risk and benefits before arriving at any conclusion and making any decisions.

What are the different types of karyotype tests?

1. The most common way to test the chromosomes is through the blood in adults, infants, and children.
2. The people who have been diagnosed with some type of cancer or blood-related disorders. The Karyotype is done through the Bone Marrow Aspiration and Biopsy.
3. A test of the fetus or unborn baby is done through Chorionic Villi Sampling (CVS).

What happens during the karyotype blood test?

The process of obtaining blood for a standard karyotype test only takes a few minutes. You can have the test done in a health care provider’s office, hospital, or laboratory. A health care provider called a lab technician usually takes blood samples.

Here’s what you can expect:

A lab technician draws blood from a vein in your arm using a thin needle. You may feel a slight sting and some mild discomfort. They inject blood into a tube and then remove the needle. He put a small bandage on your arm.

What happens during the karyotype amniocentesis and CVS?

The process is mentioned for Prenatal testing using amniocentesis or chorionic villus sampling (CVS) below.

For amniocentesis:

• You will lie on your back on the table.
• Your provider will move the ultrasound machine over your abdomen. Ultrasound uses sound waves to check the position of the uterus, placenta, and baby.
• Your provider will insert a thin needle into your abdomen and draw out a small amount of amniotic fluid.
• Amniocentesis is usually performed between 15 and 20 weeks of pregnancy.

For CVS:

• You will lie on your back on the table.
• Your provider will move the ultrasound machine over your abdomen to check the position of your uterus, placenta, and baby.
• Your provider will collect cells from the placenta in one of two ways: either through the cervix using a thin tube called a catheter or through your abdomen with a thin needle.
• CVS is usually performed between 10 and 13 weeks of pregnancy.

What happens during the bone marrow aspiration and biopsy test?

If you are undergoing treatment for a certain type of cancer or blood disorder, your healthcare provider may need to take a sample of your bone marrow. For this test:

• You will lie on your side or on your stomach, depending on which bone will be used for the test. Most bone marrow tests are taken from the hip bone.
• The site will be cleaned with disinfectant.
• You will be given an injection of an anesthetic solution.
• Once the area is numb, a health care provider will take the sample.
• For bone marrow aspiration, which is usually done first, the health care provider will insert a needle through the bone and remove bone marrow fluid and cells. You may feel sharp but less painful when the needle is inserted.
• For a bone marrow biopsy, your health care provider will use a special instrument that is twisted into the bone to take a sample of bone marrow tissue. You may feel some pressure at the site while taking the sample.

Are there any risks involved with the test?

There is some risk involved during the blood test. There can be slight pain or bruising when the needle is being inserted but these symptoms will go away quickly.

Though the Amniocentesis and CVS test is a safe procedure and done by certified fetal medicine experts there is some risk of miscarriage.

After a bone marrow biopsy, you may feel tightness or pain at the injection site. It usually goes away within a few days. Your health care provider may recommend or recommend pain relievers to help.

What do the results of Karyotype mean?

Abnormal karyotype test results may mean that you or your baby have abnormal chromosomes. It can indicate diseases and genetic disorders such as:

• Down syndrome also known as trisomy 21, causes developmental delay and intellectual disability.
• Edwards syndrome also known as trisomy 18, causes serious problems in the lungs, kidneys, and heart.
• Patau syndrome causes poor development in the womb and low birth weight.
• Turner syndrome prevents girls and women from developing feminine characteristics.

Reference :

1. Karyotype Genetic Test: MedlinePlus Medical Test. [online] Medlineplus.gov. 
2. Cleveland Clinic. 2022. Karyotype Test: Test & What Is It. [online] 
3. Ozkan E, Lacerda MP. Genetics, Cytogenetic Testing, And Conventional Karyotype.