Prenatal CGH Array
An array CGH is a technique that allows the detection of chromosomal abnormalities with a higher resolution than conventional techniques.
What is a CGH array?
Array CGH, sometimes called molecular karyotyping, is a particularly differentiated and precise screening method in genetic diagnosis. Unlike conventional chromosome analysis, it can also detect very small changes in the genome, both microdeletions (absence of a very small piece of chromosome) and microduplications (addition of a piece of chromosome).
Prenatal array CGH can only be performed in combination with amniocentesis or chorionic villus sampling.
What prenatal CHG array do we offer at Genosalut?
For prenatal array CGH we have a 60k coverage platform that detects copy number variations, as well as small deletions and duplications associated with chromosomal abnormalities in the foetus. It is also applicable to the study of abortive remains in cases of repeated abortions.
We have a CGH array platform (60k) for prenatal assessment of copy number changes in genome-wide chromosomal regions and high resolution in syndromic regions. This array allows us to analyse
- Unbalanced translocations
- Chromosomal mosaicism
- Rearrangements of pericentromeric and subtelomeric regions
- More than 290 microdeletion and duplication syndromes associated with mental retardation and autism.
Our value proposal
Prevention and peace of mind with the genetic tests of Genosalut
How can I request a CGH array?
An array CGH is indicated by a gynaecologist in one of the following cases:
- Abnormal ultrasound findings, e.g. organ malformation in combination with growth retardation or multiple malformations.
- Abnormal chromosomal findings that need to be further clarified.
- History of chromosomal abnormalities in the family.
- Family history of increased risk of developing abnormalities.
- Repeated miscarriages.
We also perform array CGH if the prospective parents have a great need for reassurance and want very detailed information about the chromosomal picture of the foetus.
The test can be done on DNA from cells obtained by:
- Amniocentesis: from 15 weeks gestation onwards
- Chorionic villus sampling: from 12 weeks gestation onwards
Cytogenetic analysis or conventional karyotyping is used to determine that the number, size and shape of an individual’s chromosomes are correct. This test is performed to rule out major alterations associated with problems such as miscarriages, malformations and/or mental retardation.
The main difference between the two tests is their resolution.
- The resolution of conventional karyotyping or cytogenetic analysis is limited and can only detect changes in the number and/or structure of chromosomes larger than 5-10 million base pairs (Mb).
- The resolution of array CGH or molecular karyotyping is much higher, as it allows the simultaneous detection of very small alterations (gains or losses of DNA fragments) responsible for more than 300 genetic syndromes associated with mental retardation, autism, heart disease and other pathologies, most of which are not detectable by conventional karyotyping.
- Positive or altered result: indicates the presence of a chromosomal abnormality. However, sometimes it may not be known whether the abnormality detected may be the cause of the abnormal ultrasound findings or what consequences it may have on the baby’s health. An additional blood test is then recommended for the parents. If a healthy parent carries the same change in the genetic material, it can usually be assumed that this variation is of no health significance.
- Normal or negative result: indicates that no chromosomal abnormality has been detected by this technique. It should be noted that there are some genetic diseases that cannot be diagnosed by array CGH, such as those caused by differences in DNA that are too small to be detected even by array CGH. In such a case, other tests (exome or genome) can be performed to dispel the doubts.
The costs of an array CGH are covered by some private insurances and sometimes depend on certain criteria (patient’s medical history, family history, abnormal findings in ultrasound scans…). You can come to us with a certificate from your doctor or with your insurance card.
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