KARYOTYPE (Chromosome Analysis)
Karyotype or Chromosome analysis is a genetic test that evaluates the number and structure of a person’s chromosome to detect the presence of various kinds of chromosome
abnormalities including most common Down’s Syndrome (Trisomy 21).
It’s considered as a gold standard test to rule out chromosome abnormalities in any person including structural abnormalities such as balanced translocations. A karyotype test
examines a person’s exact chromosome number (ploidy level) for the entire set of chromosomes and examines the structural changes if different from the normal chromosomes’ appearance.
Genetics Explained:
Humans have 46 chromosomes, present as 23 pairs. Twenty-two pairs are found in both genders (autosomes), and one pair (sex chromosome) is present as either XY (in males) or XX (in females). Chromosomes are thread like structures within each nucleus and contain
the body’s genetic codes or blueprint.
Normally All cell in the body that have a nucleus will contain a complete set of the same chromosomes, except for the reproductive cells (eggs & sperm), which contain a half set of
23. This half set is the genetic contribution that will be passed on to a child. At conception, half set from each patent combine to form a new set of 46 chromosomes in the developing
fetus.
Each chromosome contains thousands of genes in specific locations. These genes are
responsible for person’s inherited physical characteristics, and they have a profound impact
on growth, development, and function through expression of various proteins.
When is Karyotype test requested.?
- A chromosome analysis may be ordered to determine the cause of baby’s birth defect for suspected congenital (physical abnormalities) from birth for e.g. Down’s syndrome
- In unborn fetus during course of pregnancy suspected of having some chromosomal abnormalities for e.g., Downs, Patau, Edwards syndrome etc.
- Couple karyotype with history of miscarriages (recurrent pregnancy loss) to detect balanced translocations carriers to plan and further management of future pregnancies.
- In couples undergoing infertility treatment, preimplantation genetic testing (PGT-A) and suspected of chromosome abnormalities such a Klinefelter’s syndrome (47,XXY) in males or Turner Syndrome (45, X) in women and family history of chromosome abnormalities.
- In males with abnormal semen parameters in case of very low sperm countparticularly in cases of oligospermia or severe oligozoospermia (<10 million/ml)
- Confirm sex chromosomes abnormalities in cases of ambiguous genitalia or discordant sex.
- In diagnosis and management of blood cancer (leukaemia) due to acquired chromosome abnormalities for e.g., chronic myeloid leukaemia (CML) for diagnosis and treatment.
Genetic Investigations
| Common Karyotype Tests | Purpose | Sample Type | Container Type | Volume |
|---|---|---|---|---|
| Karyotyping: Blood Lympho Culture, Single | Detect chromosome abnormalities in adults/children | Peripheral Blood | Sodium Heparin Green Top -1 | 4 ml |
| Karyotyping: Blood Lympho Culture, Couple | Husband & Wife with history of recurrent pregnancy loss (RPL) | Peripheral Blood | Sodium Heparin Green Top -2 (Husband & Wife) | 4 ml Each |
| Karyotyping (KT)- Prenatal | During pregnancy to detect chromosomes abnormalities including Down syndrome | Amniotic Fluid /Chorionic Villus Sampling (CVS) | Falcon Tube -1 Sterile Container -1 | 20 ml Amniotic Fluid / CVS in transport media (from lab) |
| Karyotyping: Products Of Conception (POC) | in cases of pregnancy loss, spontaneous abortion, miscarriages, | POC in Normal Saline, prefer placental or fetal origin | Sterile Container -1 | POC sample |
| Karyotyping (KT)- Postnatal | Detect chromosome abnormalities in adults/children | Peripheral Blood / Bone Marrow Aspirate | Sodium Heparin Green Top -1 | 4 ml |
| Karyotyping: Hematologic Malignancy | to detect chromosome abnormalities in blood cancer patient for diagnosis & treatment | Peripheral Blood / Bone Marrow Aspirate | Sodium Heparin Green Top -1 | 3 ml |
