What is a conventional cytogenetic analysis or karyotype?
Each cell of our body contains DNA that is packaged inside the nucleus forming structures that we know as chromosomes, in which genetic information is stored. This information determines our appearance and controls the development of all the organs of the body. Most cells in our body contain 46 chromosomes (23 pairs inherited from the father and 23 pairs from the mother), 44 autosomes and 2 sex chromosomes (XX in women, and XY in men). The arrangement of the chromosomes in pairs of homologs is called karyotype, and is characteristic of each species. The cytogenetic analysis or conventional karyotype allows to examine that, both the number and the size and shape of the chromosomes of the fetus is “correct”, because when there is some extra chromosome (trisomy) or less, or a piece of some, the baby could be born with malformations and / or mental retardation.
How is the analysis differentiated by Molecular Karyotype (Array CGH) from the conventional karyotype?
The karyotype or conventional cytogenetic analysis has a limited resolution and only allows to detect 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 approximately 200 genetic syndromes associated with mental retardation, autism, heart disease and other pathologies, most of which are not detectable by the conventional karyotype.
Should my child be tested by CGH Microarrays?
The analysis by Microarrays of CGH is indicated in those individuals with problems of learning, behavior, physical development, intellectual disability and / or birth defects.
My son has already had other genetic tests done.
What additional results will the analysis provide us with Molecular Karyotype?
At present there are many different genetic tests that allow detecting different types of alterations that can cause different pathologies. Given that the Molecular Karyotype technique is a new technology that is able to detect chromosomal imbalances that are too small to be visualized by the conventional karyotype, it is possible that it detects a genetic anomaly, despite having previously performed other analyzes with normal results.
What are the advantages of Molecular Karyotype analysis?
The analysis by means of Molecular Karyotype in some cases allows the identification of the cause of the clinical manifestations that the patient presents and this diagnosis can be very useful to offer a better medical attention to the patient (indicate an adequate treatment to alleviate the common health problems that occur associated with the disease, as well as predict what to expect as the child grows). In addition, this diagnosis allows to study if the parents can be carriers of changes in their DNA that could suppose a greater risk of having more children with the same problems or even more serious in the future.
What type of sample is needed for the analysis?
Molecular Karyotyping is usually performed on a blood sample. However, it can also be performed on other types of samples such as DNA or cells from a skin sample, and during pregnancy, in cells of the amniotic fluid or chorionic villi (placental tissue). Your doctor will determine which sample is the most appropriate in your case.
How long will it take and who will contact me to inform me of the results?
The results are sent by email to the doctor requesting the test, 30 working days after the sample is taken. Your doctor is in charge of communicating and explaining the results and performing appropriate and specific genetic counseling if necessary.
What does an altered or positive result mean in the analysis by Molecular Karyotype?
A positive or altered result can provide a clinical diagnosis and explain the problems your child has. However, it is sometimes 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 parents or 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 that the patient presents. Given that medical research is a very active field, in all cases it is recommended that your doctor review the variants identified in the future to try to determine their possible clinical relevance based on new knowledge.
What does a normal or negative result mean in the analysis by Molecular Karyotype?
It should be noted that there are some genetic diseases that can not be diagnosed by Molecular Karyotype, this is the case of those that are caused by differences in DNA that are too small to detect even by Molecular Karyotype. Therefore, a molecular karyotype or normal Molecular Karyotype 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.
What is a genetic counselor and when his attention is necessary?
The 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 assess the risk of transmitting the disease to their children. If necessary, it can provide information about genetic tests, interpret results and supervise all additional analyzes, aids or research options within reach.
Some pregnant women can also be sent to a counselor to receive information about the risks of congenital 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, Genolife makes available through our associate doctors a highly specialized genetic counseling team, who study each case and establish in a consensual and multidisciplinary way the method of action, providing an assistance service with high added value to the consultations of the current health system.
My son was tested two years ago by Molecular Karyotype, should he undergo these tests again?
Like many other techniques, the Molecular Karyotype is a technology that is continuously evolving. For this reason, 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 you need to repeat them, as well as inform you about their cost.
Will the sample be used for other purposes after the study?
The sample will be kept anonymously for the required time and then conveniently discarded. However, if it is previously informed, it may cede its use for the investigation of new diagnostic strategies.
I have more questions about the Molecular Karyotype tests. Who can I contact?
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 (+52 662 313 91 51) or by email (email@example.com)