Karyotype – what is it? Course and price of the karyotype test

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A karyotype is a set of chromosomes that is unique to every human being. Karyotype testing is usually performed in women who have had more than one miscarriage or had a stillborn child to exclude or confirm the influence of genetic factors on pregnancy loss. The karyotype should also be performed by the father, because a miscarriage can sometimes be caused by damage to the male’s chromosome.

Karyotype – what is it?

A karyotype is a unique set of chromosomes present in every cell in the human body. The structure of the human karyotype is gender and autosomal dependent. A healthy person has 22 pairs of autosomes and sex-determining chromosomes. Women have two X chromosomes, and men have one X and one Y chromosome. People with a different karyotype structure are called chromosomal abnormalities.

Chromosome anomalies are divided into translocations (chromosomal displacements), inversions (displacements of chromosomal fragments) and deletions (chromosomal defects), in the case of changes in the number of chromosomes, it is called polyploidy.

Changes in the karyotype structure are the cause of genetic defects, and often also miscarriages or stillbirths. It often happens that the incorrect structure of the karyotype of one of the parents causes problems with getting pregnant, so in the case of a greater number of miscarriages or long-term problems with getting pregnant, karyotype tests are performed.

See: A blood test will reveal genetic defects in the fetus

Karyotype and genetics

Chromosomes are the thread-like structures in the nucleus of cells that we inherit from our parents and that contain our genetic information in the form of genes. Genes direct the synthesis of proteins in our body, which determines how we look and function.

Almost all of them usually have 46 chromosomes, 23 of which we inherit from our mother and father, respectively. The first 22 pairs are autosomes that define our unique biological and physiological characteristics. The 23rd pair is made up of sex chromosomes (known as X or Y).

Any mistake in genetic coding can affect the development and the way our body works. In some cases, this may put us at increased risk of disease and genetic defects. The karyotype makes it possible to detect them.

Chromosomal defects occur when a cell divides during fetal development. Any breakdown in the reproductive organs is called meiosis. Any division that occurs outside the reproductive organs is called mitosis.

Read: Sudden Infant Death from Defective Hippocampus Development

Karyotype – What Can It Indicate?

The karyotype characterizes the chromosomes by their size, shape, and number to identify both numerical and structural defects. While numerical abnormalities are those with too few or too many chromosomes, structural abnormalities can cover a wide range of chromosomal defects, including:

1. deletions – in which part of the chromosome is missing,
2. translocations – where the chromosome is not where it should be,
3. inversions – in which part of the chromosome has turned in the opposite direction,
4. duplications – in which part of the chromosome is accidentally copied.

Karyotype – chromosomal abnormalities

Some of us are born with an extra or missing chromosome. If there are more than two chromosomes and there should only be two, this is called trisomy. If a chromosome is missing or damaged, then it is called monosomy.

Some of the numerical abnormalities that a karyotype can detect are:

1. Down syndrome (trisomy 21), in which an extra 21 chromosome causes characteristic facial features and intellectual disability,
2. Edward’s syndrome (trisomy 18), in which an extra 18 chromosome translates into a high risk of dying before one birthday,
3. Patau’s syndrome (trisomy 13), in which an extra chromosome increases the likelihood of heart problems, intellectual disability, and death before the age of one
4. Turner syndrome (monosomy X), in which girls are missing or damaged X chromosome translates into shorter height, intellectual disability and an increased risk of heart problems.
5. Klinefelter’s syndrome (XXY syndrome), in which an extra X chromosome in boys can cause infertility, learning disabilities and underdeveloped genitals.

Structural abnormalities are not as commonly seen or identified as trisomes or monosomes, but they can be just as serious. Examples of structural irregularities include:

1. Charcot-Marie-Tooth disease, caused by duplication of chromosome 17, leading to reduced muscle size, muscle weakness, and problems with motor skills and balance.
2. Chromosome 9 inversion associated with intellectual disability, facial and skull malformations, infertility and recurrent pregnancy loss,
3. Cri-du-Chat syndrome, in which a deletion of chromosome 5 causes delayed development, small head size, learning disorders and characteristic facial features
4. The Philadelphia chromosome, caused by the reciprocal translocation of chromosomes 9 and 22, carries a high risk of chronic myeloid leukemia,
5. Williams syndrome, in which the translocation of chromosome 7 causes intellectual disability, heart problems, characteristic facial features and open, engaging personalities.

Read: Diseases detected in the womb – diagnosis and prenatal examinations indicated

Construction of the karyotype and miscarriage

Research indicates that karyotype abnormalities account for about 16 percent of miscarriages. It is assumed that miscarriages in the first trimester of pregnancy are associated in 2-4% of cases with an abnormality in the structure of the karyotypeand the vast majority of early miscarriages are of a different nature.

Changes in the human karyotype responsible for miscarriages are most often translocations (displacements of chromosome fragments) or the so-called Robertson translocations (displacements of entire chromosome arms).

Another common cause of miscarriages and complications in pregnancy is mosaicism. Mosaicism consists in having two different cell lines, in the absence of the X chromosome, Turner syndrome occurs. In women diagnosed with mosaicism, the risk of miscarriage is as high as 50 percent.

The editorial board recommends: The eight most common causes of miscarriage

Karyotype – how is the test done?

The human karyotype is tested on the basis of blood samples. You do not need to prepare for the test, but the waiting time for the results is up to approx. 3 weeks. The human karyotype test is a cytogenetic test, i.e. the appropriate number of cells from the blood sample must be grown in the laboratory in order to obtain the result. On the basis of the cultured cells, the description and assessment of the correct development of the chromosomes of the examined person is made.

The karyotype test is performed in pregnant women who have had abnormalities in the fetus during ultrasound examination or in those who had previously had a miscarriage. Amniotic fluid samples are advocated for karyotype testing. By examining the karyotype, it is possible to determine whether the child is a carrier of the genetic mutation that is responsible for the abnormalities found, or whether the causes should be looked for elsewhere.

Karyotype test – test price

The price of a karyotype test varies between PLN 300 and PLN 500 and depends on the city where the patient wants to undergo the test. It is possible to reimburse the karyotype test, but only if the patient meets certain conditions. The karyotype test will be reimbursed to patients with clear indications for testing, such as previous miscarriage, stillbirth or age over 35. Karyotype analysis can also be reimbursed for couples who have had genetic mutations among family members or have had miscarriages and stillbirths.

The karyotype as part of the NHF reimbursement is also tested in couples who, despite over a year of active sexual activity, are unable to fertilize.

If the doctor does not consider it necessary to perform a karyotype test, the patient must bear the cost of the test herself.