A DNA microarray is a device, similar to a microscope slide, which contains on its surface hundreds of thousands of DNA fragments (like a brush) that can determine the number of copies of hundreds of thousands of positions in the human genome . It is known that when the number of copies of certain fragments of the human genome are altered genetic diseases appear, such as Down syndrome (caused by having 3 copies of chromosome 21), or DiGeorge syndrome (caused by the deletion of a fragment of chromosome 22).
The cytogenetic analysis or conventional karyotype allows to examine that both the number and the size and shape of the chromosomes of an individual is “correct”, because when there is one extra (trisomy) or one less chromosome, or a large piece of a chromosome is missing, the person could present malformations and / or mental retardation.
The karyotype or conventional cytogenetic analysis has a limited resolution and only allows the detection of changes in the number and / or structure of chromosomes of a size greater than 5-10 million base pairs (Mb). However, with the molecular karyotype (CGH microarrays) it is possible to simultaneously detect gains or losses of DNA fragments responsible for more than 300 genetic syndromes associated with mental retardation, autism, heart disease and other pathologies, mostly not detectable by the conventional karyotype.
The analysis by microarrays of CGH is indicated in children or adults with developmental disorders (intellectual disability, autism …) with or without associated malformations.
At present there are many different genetic tests that allow the detection of different types of alterations that can cause different pathologies. Since the CGH array technique is a new technology that is capable of detecting chromosomal imbalances that are too small to be visualized by the conventional karyotype, it is possible that it detects a genetic anomaly, despite other analyses performed previously had delivered normal results.
The analysis by array CGH in some cases allows the identification of the cause of the clinical manifestations presented by the patient and this diagnosis can be very useful to offer better medical care to the patient (indicate an adequate treatment to alleviate the common health problems that occur associated with the disease, as well as to predict what to expect as the child grows). In addition, this diagnosis allows studying if parents can be carriers of changes in their DNA that could imply a risk of having more children with the same or even more serious problems in the future.
The CGH array analysis is performed from DNA, which is usually obtained from a blood sample. However, it can also be done from saliva, cells from a skin sample, … and during pregnancy, from cells of the amniotic fluid or chorionic villi (placental tissue). Your doctor will determine which sample is the most appropriate in your case.
The results are ONLY sent to the doctor requesting the test, a few weeks after taking the sample. Your doctor will be in charge of communicating and explaining the results, and performing appropriate and specific genetic counseling if necessary.
A positive or altered result can help you reach an accurate clinical diagnosis and explain the problems your child has. However, sometimes it is possible that at the time of the analysis it is unknown whether the detected alteration is the cause of the clinical manifestations present in the patient, and that in order to interpret the results it is necessary to carry out additional studies in the patient, in their parents or in other family members. It can happen that even after several additional studies, it is impossible to confirm if the presence of a certain variant is the cause of the pathologies present in the patient. Given that medical research is a very active field, in all cases it is recommended that your doctor reviews the variants identified in the future to try to determine their possible clinical relevance based on new knowledge.
It should be noted that there are some genetic diseases that can not be diagnosed by CGH array, this is the case of those that are caused by differences in DNA that are too small to detect even by CGH array. Therefore, a molecular karyotype or normal CGH array analysis does not rule out the existence of a certain genetic disease. Your child’s doctor will assess and discuss the results obtained and the possibility of performing other tests to diagnose your child’s illness.
A genetic counselor is a health professional who can help a person or family understand the risk of developing a genetic disease (for example, cystic fibrosis, cancer or Down syndrome), educate people about that disease and evaluate the risk of transmitting the disease to their children. If necessary, they can provide information on genetic tests, interpret results and supervise all additional analyses or research options within reach.
Some pregnant women can also be sent to a counselor to receive information about the risks of birth defects associated with their pregnancy, or to help them interpret results of genetic screening tests performed during pregnancy.
In order to offer complete assistance, if required, qGenomics Clinic offers a highly specialized genetic counseling team, consisting of several genetic advisors and clinical geneticists who study each case and establish the way of action in a consensuated and multidisciplinary manner, providing a high-added-value assistance service to the current health system.
Like many other techniques, the CGH array is a technology that is continuously evolving. Therefore, and depending on how long ago the tests were performed on your child, it may be indicated to repeat the tests. In any case, your doctor or genetic counselor can help you decide if it is necessary to repeat them, as well as inform you about their cost.
The sample will be kept anonymously for the required time and then conveniently discarded. However, if you give your consent, you may assign its use for the research of new diagnostic strategies.
Your doctor can tell you about all the details of this test.
However, for any questions, you can contact us through our telephone assistance department (932 301 270) or email at firstname.lastname@example.org