What Is the Difference Between the CGTs Available on The Market?

Carrier genetic tests (CGTs) are genetic screening tests used to detect possible alterations in each parent’s genes that could be passed on to their offspring. They are recommended before conception, whether naturally or through assisted reproduction treatments, with the aim of reducing the risk of transmitting hereditary genetic diseases.

What Are CGTs for? 

According to the WHO, between 5,000 and 8,000 hereditary genetic diseases have already been identified. However, the presence of a mutated gene in one of the parents does not mean that their offspring will develop the disease.

In recessive genetic diseases, both parents must carry the mutation in the causative gene for the child to develop the disease.

For this reason, knowing the mutations that both parents carry allows for an assessment of the risk of transmitting a genetic disease and making informed decisions before conception.

What Happens If Both Parents Are Carriers of the Same Mutation? 

If both parents are carriers of a mutation in the same gene associated with a disease, there is a 25% risk in each pregnancy that the baby will inherit both mutated copies and develop the disease.

In this case, it is recommended for the couple to undergo in vitro fertilization (IVF) with preimplantation genetic diagnosis (PGD). This way, only embryos that are genetically healthy are selected for transfer.

Another option is to use a gamete donor, either sperm or egg donation, who is not a carrier of the mutation.

When Should a CGT be Performed? 

A CGT can be performed on any couple, regardless of whether they have fertility problems or not. However, it is especially recommended for couples who:

• Have a family history of genetic diseases.
• Are undergoing assisted reproduction treatment.
• Are undergoing treatments with egg donation or sperm bank.

What Types of CGTs Are Available on the Market? 

There are several types of CGTs, ranging from basic tests that analyze between 20 and 100 recessive diseases to more advanced ones that can study up to 1,500 diseases.

They also differ in the technology used. Some tests use PCR to detect mutations in specific genes, while others use massive sequencing (NGS) to analyze thousands of genes or microarrays to identify genetic variations in multiple regions of DNA. The time and cost of CGTs vary depending on the number of genes analyzed. The more genes studied, the higher the cost and the longer the time required to obtain the results.