A karyotype test is a simple blood test done to examine the shape, size and number of chromosomes present in the cells of the blood. Abnormal positioning, extra or missing chromosomes can widely affect the growth, development and functionality of many body parts. Karyotypes are typically extracted from blood cells, fetal skin cells or the bone marrow cells.
Why is karyotype test done?
The reasons behind karyotyping are plethora. Some of them are as follows:-
- To check whether the chromosomes of an individual have a change which can be passed to his/her child.
- To check whether a defect in a chromosome is prevent a woman from conceiving.
- To check for the presence of a chromosome defect in a fetus
- To check for the reasons behind defect in a baby’s growth and development.
- Determine the right treatment for certain types of cancers.
- For identifying the sex of an unborn baby.
How is it done?
A karyotype test can be done using almost any cell or tissue of the body. However, in most cases, a sample of blood is taken from the vein for testing. In case of pregnancy, a sample of amniotic fluid or that of placenta may be extracted for examination.
Blood Sample from Vein – In this case, a sample of blood is drawn from one of the veins of the body, usually those on the arm. The sample is collected in special tubes which are then sent to the laboratory for in-depth examination and evaluation.
Cell Sample from Fetus – In this type of karyotype test, a few cells are extracted from the fetus with the help of amniocentesis or chorionic villus sampling method. These are then sent to the laboratory for in-depth examination and evaluation.
Cell Sample from Bone Marrow – A bone marrow biopsy is conducted to extract a sample of bone marrow for karyotype testing. Similar to the above two methods, the sample is sent to the laboratory for in-depth examination and evaluation.
How to Interpret the Results?
Interpreting karyotype test results is simple and easy. In case of normal results, the following may be noted:-
- Females – 44 autosomes along with 2 sex chromosomes marked as XX. A total of 46 chromosomes (XX)
- Males – 44 autosomes along with 2 sex chromosomes marked as XY. A total of 46 chromosomes (XY)
Any deviation from the above mentioned normal range indicated the presence of abnormality. This means:-
- More than or less than 46 chromosomes.
- Abnormal shape or size of one of more than one chromosome
- A pair of chromosome is either broken or separated in an inappropriate manner.
- The presence of some kind of genetic syndrome or condition such as
- Down syndrome
- Klinefelter syndrome
- Philadelphia chromosome
- Trisomy 18
- Turner syndrome
In addition to this, chemotherapy can cause the chromosome to break down which in turn may affect the result of a karyotype test.