GeneScreen Complete test

 

Each of us carries at least one gene that causes a genetic disease. Carriers are usually healthy but have a significant risk of passing the severe genetic disease on to their children. Without the GeneScreen Complete test, these diseases may go undetected, potentially leading to health issues in the child.

The GeneScreen Complete test is a genetic disease carrier screening test that provides you with the reassurance of finding partners with a higher risk of having a genetically affected child together. The GeneScreen Complete test evaluates the carrier of an autosomal recessive or X-linked disease in a woman and/or her partner. Such gene mutations can cause 2,100 different monogenic diseases in their shared children, which cannot be detected by prenatal ultrasound or in the immediate postnatal period, as most of them manifest only in the first years of the child's life.

The GeneScreen Complete test empowers you to take proactive steps when planning a pregnancy. While a genetic suitability test has not been performed before conception, we recommend that it be performed immediately after the pregnancy is detected and the child's viability is assessed in the 8th week of pregnancy.

 

How can healthy parents pass on a genetic disease to their children?
 

There are two main types of inheritance that can result in healthy parents having a child with a severe genetic disease: autosomal recessive inheritance and X-linked inheritance.

 

What is autosomal recessive inheritance?
 

Some hereditary diseases follow an autosomal recessive pattern of inheritance. This means that for the genetic disease to manifest, a child must inherit two altered genes - one from each parent - from a specific gene pair. If a child receives one altered gene and one normal gene, the normal gene usually compensates for the altered one. In such cases, the child becomes a carrier of the genetic change but does not exhibit the disease.
 

Common autosomal recessive diseases include cystic fibrosis and spinal muscular atrophy.

 

How are recessive diseases inherited?

Recessive diseases are inherited when both parents carry the same gene mutation. They randomly pass on either a normal or mutated gene to their child.

 

Every child whose parents both carry the same mutated gene has a 25% (1 in 4) risk of inheriting the mutated gene from both parents and developing a hereditary disease. Conversely, there is a 75% (3 in 4) chance that the child will not have a hereditary disease.
 

Additionally, in 50% (2 in 4) of cases, a child may inherit one mutated gene from their parents. In this situation, while the child does not have the disease, they become a carrier, similar to their parents. Moreover, in 25% (1 in 4) of cases, the child may receive two normal genes from the parents, meaning they will neither develop a genetic disease nor be a carrier of it.
 

For autosomal recessive diseases, which are caused by genes located on autosomal chromosomes (chromosomes 1-22), the diseases can manifest in both boys and girls. These risks are present in every pregnancy.

Understanding X-linked recessive inheritance is crucial in comprehending the complexities of genetic diseases.
 

The X chromosome contains several genes that are necessary for growth and development. The Y chromosome is much smaller and also has fewer genes. Females have two X chromosomes (XX), and if there is a change in one X chromosome, a normal gene on the other X chromosome can compensate for the change. In this case, the girl is an outwardly healthy carrier of X-linked disease. A compensating gene is a normal gene on the other X chromosome that can 'make up for' the altered gene, preventing the disease from manifesting. Women who carry the disease are not sick, but carry a gene with changes. For some of these diseases, the course of the disease is milder in women.

Boys, with their XY chromosomes, face a different genetic landscape. If a gene on the X chromosome is altered, they lack a second compensating gene, leading to the manifestation of the disease. This stark reality underscores the importance of understanding and addressing X-linked recessive diseases.

More common X-linked diseases are Duchenne muscular dystrophy and fragile X syndrome.

 

How are X-linked diseases inherited through female carriers?

When a female carrier gives birth to a son, the gene inheritance is a game of chance. She passes on either an X chromosome with a normal gene or an X chromosome with an altered gene. This means all sons of a carrier mother have an equal 1 in 2 (50%) chance of inheriting the mutated gene and falling ill. However, in 1 out of 2 cases (50%), the son receives a normal gene and remains healthy. This pattern of inheritance is consistent for all sons.

If a female carrier has a daughter, she will pass on the X chromosome with the normal gene or the X chromosome with the altered gene to her daughter. All daughters have a 1 in 2 (50%) chance of inheriting the mutated gene. When this happens, the daughter is the bearer of change just like the mother. However, there is also a 1 in 2 (50%) chance that the daughter will inherit a normal gene. In this case, the daughter is not a carrier and does not have the disease. This inheritance pattern applies to all daughters.

Is my child at risk for diseases that do not run in our family?
 

Yes, they may be. Generally, children can be born with certain diseases even in families where the diseases have never occurred before. This risk remains, even if the parents have had healthy children in the past. Consequently, the birth of a child with a serious condition can often come as a surprise to the family. In Estonia, it is theoretically possible to identify a genetic disease that can be screened using GeneScreen Complete in about 30 children each year.

 

Is it possible to diagnose the diseases you are looking for during a prenatal ultrasound?

It's a surprising fact that most babies with hereditary genetic diseases appear healthy at birth. These diseases, which cannot be detected prenatally on ultrasound examinations, typically do not present problems during pregnancy or childbirth. The symptoms usually appear in the first years of life.

How common are these genetic conditions?

While it's true that hundreds of inherited genetic diseases can potentially affect a child's health, it's important to remember that the vast majority of them are extremely rare.
 

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With the GeneScreen Complete test, which covers nearly 2,100 monogenic diseases, the combined disease incidence is one in four hundred fetuses (1 in 400). This figure is higher than the incidence of Down syndrome, providing a comprehensive understanding of potential genetic health risks.

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It's a common misconception that most couples who have an affected child have a family history of the disease. In reality, many were not aware of their higher chance of having a genetically affected child. This is because a healthy couple can unknowingly pass on a genetic disease to their child. Therefore, genetic disease carrier screening is a crucial step for everyone, empowering them to make informed decisions about their family's health.

 

What are the alternatives to the GeneScreen Complete test?

The GeneScreen Complete test is a valuable tool for the detection of monogenic diseases inherited from parents. However, it's important to note its limitations. The test cannot detect fetal chromosomal disorders, microdeletions, or gender. It also does not provide information about the anatomical structures of the fetus or potential pregnancy complications, such as preeclampsia and fetal growth retardation.

If you're seeking a more comprehensive understanding of your baby's health, the WISE test is an excellent option. It not only covers the monogenic diseases inherited from the parents that the GeneScreen Complete test can detect, but also includes monogenic diseases that can occur in the fetus during pregnancy, chromosomal pathologies, microdeletions, and congenital malformations of the fetal organ structures. It also assesses the risks of complications during pregnancy, providing a thorough picture of your baby's health.

For women who want the highest level of confidence in their baby's health, the amniocentesis is a powerful tool. It can detect over 99% of all chromosome and gene disorders that cannot be detected by the GeneScreen Complete test or other screening tests, providing a comprehensive and accurate assessment of your baby's health.

 

When will I know my test results?

You will find out the test results 35 days after the blood tests.

 

What results can I expect from the GeneScreen Complete test?

The GeneScreen Complete test tells you whether you carry an autosomal recessive or X-linked disease that can be assessed by this test. Men are not tested for X-linked diseases.

A negative test result significantly reduces the chance that you are a carrier of a genetic disease. Still, you must know that the GeneScreen test does not detect all genetic diseases.

 

Does a positive screening test mean that the child has an investigational disease?
 

It doesn't mean. The GeneScreen Complete test examines the parents, not the fetus growing in the womb. In the case of a positive GeneScreen Complete test response, a medical geneticist must be consulted. To confirm or rule out the presence of a genetic disease in the fetus, the woman must undergo a diagnostic test, for example, a chorionic biopsy, an amniotic fluid test, or a diagnostic test performed on the newborn's venous blood after birth.
 

What empowering steps can we take if we are more likely to have a child with a genetic disease?

If you found out before becoming pregnant that you and your partner carry the same autosomal recessive genetic disease or you are a carrier of an X-linked disease, it is possible to:
 

 

•  natural conception and testing of the child after birth;
•  natural conception and performing a chorionic biopsy during pregnancy to detect a genetic disease of the fetus;
•  in vitro fertilization (IVF) and preimplantation embryo testing for monogenic diseases (PGT-M) to transfer a genetically healthy embryo into the uterus;
•  in vitro fertilization using sperm, eggs or embryos from a genetically healthy donor;
•  adoption;
•  abandon the plan to have children;

If you are carrying an X-linked recessive disease, it is recommended to do the Panorama test or the KaryoPlus test to assess the gender of the fetus. These tests can determine the gender of the fetus and whether it is affected by a genetic disease. For X-linked diseases, only boys are affected, so knowing the gender can help you make informed decisions about the pregnancy. No additional diagnostic tests are required for female fetuses.

Suppose you only found out during pregnancy that you and your partner carry the same genetic disease or you are a carrier of an X-linked disease. In that case, it is possible to perform a diagnostic chorionic biopsy or amniocentesis to detect the fetal genetic disease.

In the case of a sick child, it's crucial to remember that you have the right to decide whether to terminate the pregnancy or continue it. In the case of continuing the pregnancy, it's important to prepare yourself emotionally for the birth of a sick child. We're here to support you through this process.

 

What should I do if I am a carrier of a genetic disease or an X-linked disease?

By discussing your genetic status with your family and considering the GeneScreen Complete test, you're not just making a decision for yourself. You're potentially influencing the health of future generations in your family. This proactive approach can be crucial for those who already have children or who plan to have children in the future.

 

Who can be tested, and when?

To detect autosomal recessive diseases, the GeneScreen Complete test is performed on both partners. For X-linked diseases, a woman's test is sufficient. The GeneScreen test is ideally done before pregnancy, but it can also be done after the 8th-week ultrasound for pregnancy detection and viability assessment. This flexibility allows you to plan your testing at a time that suits you best. If you want to know the duration of your pregnancy, please visit our pregnancy calculator.

How is the GeneScreen Complete test performed?
 

The GeneScreen Complete test examines your and your partner's DNA (genetic material). This test does not examine fetal DNA. The GeneScreen Complete test detects whether you or your partner do not carry the genetic disease you are looking for based on the DNA obtained from the blood sample.

The GeneScreen Complete test is a noninvasive prenatal screening test that is completely safe for you and your baby. To perform the test, a blood sample is taken from your arm and your partner's arm, which is then sent by express courier to the Eurofins Genoma laboratory in Rome, Italy, for DNA extraction and next-generation sequencing (Next-Generation Sequencing).

Who can benefit from the GeneScreen Complete test?
 

•  Healthy parents-to-be who are planning a pregnancy or are in the early stages of pregnancy
•  Couples of specific ethnic backgrounds or consanguineous marriages may have a higher risk of genetic disease.
•  A couple planning a pregnancy if one or both have family members with mental retardation or genetic diseases.
•  Women are planning in vitro fertilization with donor gametes to select a donor who does not carry the same genetic disease as the woman herself or her partner.

What genetic diseases can I find when I take the GeneScreen Complete test?

 

Diseases detected by the GeneScreen test

 

If you are pregnant, before giving the GeneScreen Complete test, we will perform an ultrasound examination to detect pregnancy and assess viability.

Most couples who take the GeneScreen Complete test find out they do not share a genetic disease that could be passed on to their child—this can be very encouraging.

 

Tests for chromosomal and genetic diseases