Also Known As: Cytogenetics, Cytogenetic Analysis, Chromosome Studies, Chromosome Karyotype, Karyotyping.
Why the Test is Needed?
To determine genetic cause for intellectual disability, chromosomal abnormalities, congenital anomalies, infertility, miscarriage, stillbirth, and ambiguous genitalia.
Chromosome cheek looks for changes or abnormalities in the chromosomes that make up our body's DNA or genetic road map. Our chromosomes are found in the inner part of our cells, called cell nucleus. They contain all the genes that have been passed down to us from our mother and father.
Each person normally has 23 pairs of chromosomes in each cell (23 pairs = 46 chromosomes). One of these pairs carries chromosomes called the X and Y chromosomes, which determine whether a person will be male or female. If persons are male, they have an XY pair. If persons are female, they have an XX pair. The other 22 pairs are called autosomes.
Abnormalities in patient chromosomes help healthcare providers diagnose many medical conditions. In some cases, patient chromosomes can help healthcare provider predict a medical problem before patient even have symptoms. Chromosome studies done on a developing baby inside a mother's womb can predict problems that a baby may be born with or develop later in life.
Some chromosomal disorders that may be detected include:
- Down syndrome (Trisomy 21), caused by an extra chromosome 21; this may occur in all or most cells of the body.
- Edwards syndrome (Trisomy 18), a condition associated with severe mental retardation; caused by an extra chromosome 18.
- Patau syndrome (Trisomy 13), caused by an extra chromosome 13.
- Klinefelter syndrome, the most common sex chromosome abnormality in males; caused by an extra X chromosome.
- Turner syndrome, caused by missing one X chromosome in females.
There is 99+% accuracy in diagnosing Down syndrome and most other gross chromosomal aberrations including neural tube defects such as spina bifida. Amniocentesis can be used to discover the presence of about 400 specific genetic abnormalities in a fetus.
Reasons for Referral:
When pregnancy screening tests are abnormal; whenever signs of a chromosomal abnormality-associated disorder are present; as indicated to detect chromosomal abnormalities in a person and/or detect a specific abnormality in family members.
Whole EDTA blood
Fetus before birth. This is done through either:
- Chorionic vilius sampling, which takes place about 11 weeks into pregnancy.
- Amniocentesis, which is usually done about 16 weeks into the pregnancy.
No test preparation is needed.
Test Done by QFPCR (Quantitative Fluorescence-Polymerase Chain Reaction)