Definition & Overview

Comparative Genomic Hybridization (CGH), also known as array CGH (aCGH) and chromosomal microarray analysis (CMA), is a technique used to analyze the human genome to look for abnormalities that commonly lead to a variety of diseases or the failure of a foetus to develop properly.

CGH, which is now a popular method in reproductive medicine to determine the quality of an egg or embryo, is also commonly used in infant screening, diagnosing developmental delays in children, and analyzing diseases, such as malignant tumours.

In reproductive health, CGH is often combined with in vitro fertilization (IVF) to diagnose and treat infertility and repeated pregnancy losses (recurrent miscarriage). By studying the genetic structure of an embryo in culture, doctors can select which embryos have the highest chance of progressing into full term and developing into a healthy baby.

As a diagnostic procedure, CGH is used to diagnose a variety of medical conditions, such as mental health retardation in children and adults, evaluation of unexplained epilepsies, diagnosing psychiatric disorders, and evaluating neurodegenerative disorders.

Who Should Undergo & Expected Results

Although CGH is an excellent technique for diagnosing and treating a variety of disorders, health insurance providers may only cover the cost of the procedure if it is used to treat specific disorders. Before considering the procedure, you should inquire if your provider will cover the costs.

Most providers will cover CGH costs if the procedure is used to diagnose and treat genetic abnormalities in children, and evaluate the cause of stillbirth or an intrauterine foetal demise, wherein the results would be beneficial to the overall health of the member.

CGH is largely beneficial for women who have recurrent miscarriages. Undergoing such procedure will improve the woman’s chances of having a healthy baby. It is also recommended for older women who still want to have a baby but are concerned about the risks of the baby developing certain medical conditions, such as Down’s syndrome.

How Does the Procedure Work?

The essence of Comparative Genomic Hybridization lies within its name, which is to compare genomes through a method called hybridization. Hybridization, in simple terms, is combining two objects to identify their distinct differences.

The basic principle of CGH is to compare a genome test sample with a reference sample obtained from the same organism. A genome consists of a complete set of genes that contain all the information needed for an organism to build. When the two samples are combined through hybridization, the researcher can identify chromosomes that have been duplicated or deleted. The results would then indicate the likelihood of a certain disease or abnormality from developing.

Researchers have found that many diseases and abnormalities can be identified in the arrangement of these genes. By studying the genes of an embryo, they can identify embryos that have a higher likelihood of developing an abnormality or disease and the ones that have a better chance of progressing into a healthy baby.

Possible Risks and Complications

While CGH does have a variety of benefits, it also presents some risks because of its limitations. One of those risks is that it cannot guarantee that an embryo will, in fact, develop into a healthy baby. CGH may be able to detect certain diseases, but will not be able to detect all types of birth defects nor identify every genetic problem that may arise. This is also true when the procedure is used as an infant screening method.

CGH is limited to analyzing differences in copy number variants of chromosomes. While some diseases and disorders can be identified by analyzing the copy number variants, not every type of genetic disorder can be identified by such method.

Additionally, many medical associations, such as the American Academy of Paediatrics (AAP) consider CGH as an “emerging technology”, which would mean that the process still has room for plenty of improvement.

It’s important to understand that in its present form, CGH can only identify the risks of a certain disease or abnormality. It may also be able to provide an explanation of mental health conditions that were previously unexplainable.

Therefore, the main risk of such a procedure is uncertainty, which can lead to anxiety or false hopes. Nevertheless, the procedure is promising and is being developed rapidly. There is a possibility that the procedure could result in the development of new treatment methods for a wide variety of diseases and abnormalities that involve the human genome.

How Does the Procedure Work?

The essence of Comparative Genomic Hybridization lies within its name, which is to compare genomes through a method called hybridization. Hybridization, in simple terms, is combining two objects to identify the distinct differences.

The basic principle of CGH is to compare a genome test sample with a reference sample obtained from the same organism. A genome consists of a complete set of genes that contain all the information needed for an organism to build. When the two samples are combined through hybridization, the researcher can identify chromosomes that have been duplicated or deleted. The results would then indicate the likelihood of a certain disease or abnormality from developing.

Researchers have found that many diseases and abnormalities can be identified in the arrangement of these genes. By studying the genes of an embryo, they can identify embryos that have a higher likelihood of developing an abnormality or disease and the ones that have a better chance of progressing into a healthy baby.

Possible Risks and Complications

While CGH does have a variety of benefits, it also presents some risks because of its limitations. One of those risks is that CGH cannot guarantee that an embryo will in fact develop into a healthy baby. CGH may be able to detect certain diseases, but will not be able to detect all types of birth defects nor identify every genetic problem that may arise. This is also true when the procedure is used as an infant screening method.

CGH is limited to analyzing differences in copy number variants of chromosomes. While some diseases and disorders can be identified by analyzing the copy number variants, not every type of genetic disorder can be identified by such method.

Additionally, many medical associations, such as the American Academy of Paediatrics (AAP) consider CGH as an “emerging technology”, which would mean that the process still has room for plenty of improvement.

It’s important to understand that in its present form, CGH can only identify the risks of a certain disease or abnormality. It may also be able to provide an explanation to mental health conditions that were previously unexplainable.

Therefore, the main risk of such a procedure is uncertainty, which can lead to anxiety or false hopes. Nevertheless, the procedure is promising and is being developed rapidly. There is a possibility that the procedure could result in the development of new treatment methods for a wide variety of diseases and abnormalities that involve the human genome.

References:

  • United States National Library of Medicine – National Institute of Health
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