Definition - what is a genetic test?

Genetic tests play an increasingly important role in today's medicine, as they can be used as diagnostic tools and for planning therapy for many diseases. A genetic test analyzes a person's genetic makeup to find out whether there are any hereditary diseases or other genetic defects. For example, you can have research carried out to determine whether you are more likely to develop Alzheimer's disease or whether you have a genetic risk for certain types of tumors.

A genetic test can therefore uncover diseases that are already present and thus confirm a suspicion, or show an increased risk for specific diseases. In the latter case, however, the disease does not necessarily occur in every gene carrier. Genetic tests are particularly popular nowadays during pregnancy in adolescent children in order to identify possible diseases or disabilities in advance.

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When should I do a genetic test?

In principle, there are two medically relevant types of reasons why genetic tests should be carried out:

  • Diagnostic genetic tests: Here, existing congenital diseases or genetic defects and their cause are identified, as well as one's own ancestry either as part of a paternity test or to determine the origin of different ethnic groups.
    One example of this is cystic fibrosis, which is initially suspected and can then be confirmed in a genetic test. Furthermore, genetic tests can be carried out on certain human traits in the context of medical diseases or therapies in order to plan a therapy. The genetic tests in advance can provide indications of a possible response to therapy or a susceptibility to certain problems in treatment.

  • Predictive genetic tests: The probability of the occurrence of a certain disease in the course of life in a (still) healthy person should be predicted. For family planning, in the case of known familial diseases, genetic counseling can also be used to predict the probability of the inheritance of various disease characteristics in the offspring. In cancer diagnostics in particular, various genetic factors can be determined that indicate that a certain cancer such as colon or breast cancer is becoming more likely.

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These hereditary diseases can be determined in a genetic test

Hereditary diseases can have very different mechanisms of origin and can therefore be difficult to diagnose. There are so-called “monoallelic” genetic diseases that are 100% triggered by a known defective gene. On the other hand, several genes in combination can cause the disease or a genetic change can only be one factor in the development of a multifactorial disease. The prerequisite for determining a genetic defect is that the gene and the genetic disease are known and specifically examined. A suspected diagnosis with evidence of a defective gene is necessary for this.

It is very difficult to compile a list of all diseases, because new genes are constantly being added that are used to predict diseases. It should also be kept in mind that for many diseases the statement is no guarantee that the disease will occur.

  1. Chromosomal diseases: these include diseases that develop in the womb in the very early stages. Often there is already a maldistribution on the maternal or paternal side before fertilization, which then leads to an incorrect number of chromosomes in the fetus. These diseases can often be tested during pregnancy or later. There are around 5000 diseases, of which around 1000 can be diagnosed during pregnancy. Classic examples are: Trisomy 13, 18 and 21 as well as Klinefelter syndrome (47, XXY), Turner syndrome (45, X), Cri-du-chat syndrome, phenylketonuria, cystic fibrosis, Marfan's syndrome, various muscular dystrophies and many more .

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  2. Tumor markers: They do not provide direct information about the occurrence of a disease, but serve as a predictive value in order to be able to find a possible tumor more quickly by having regular preventive examinations and check-ups due to an increased risk.

  3. variable expressivity: diseases can also occur later in life that have never caused a symptom. In diseases such as Huntington's disease, the disease characteristic is present (penetrance), but the disease usually only breaks out in middle age (expressivity). 100% of this condition develops if one does not otherwise die before the time of symptoms. Since some diseases only show up late, it often makes sense to have children tested for diagnostic reasons to see whether they have the characteristic before symptoms develop.

execution

preparation

Anyone who would like to have a genetic test carried out must first attend a genetic counseling in Germany. A consultation is carried out with a doctor who has been trained in human genetics or who has an additional qualification. It makes sense to think about your family tree beforehand at home.Questions about the diseases of other blood relatives are usually asked, so it is wise to find out more about the family beforehand.

As a rule, the genetic test is preceded by other diagnostic procedures to establish a suspected diagnosis. Before genetic testing, extensive information must be provided about the risks and consequences of genetic testing. In addition to medical risks, the possible outcomes and the resulting medical or psychological consequences must be discussed. No genetic test can be carried out without the consent of those affected.

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Genetic testing can then confirm the diagnosis. For this purpose, materials must be obtained that contain the genetic material. In most cases, a simple blood sample is enough to examine the cells it contains. For molecular genetic tests, however, nucleated cells are needed, which can be obtained, for example, by swabbing cells from the oral mucosa or from the bone marrow.

procedure

After the genetic counseling, which is binding in the Genetic Diagnostics Act, in which a full explanation of the process takes place, a declaration of consent is signed. Then the sample is taken in the form of saliva with a cotton swab in the mouth. Alternatively, you can use blood or other materials such as hair. However, only saliva and blood / umbilical cord blood are common. The samples are processed and examined in a laboratory.

Various tests can be carried out in the laboratory with the help of some biochemical processes in order to be able to show certain genetic errors or gene sequences. The best known test is the so-called "PCR", short for the "polymerase chain reaction". In order to carry out the test, it must be known in advance which gene sequence is being searched for in order to identify whether this gene segment is present or not. This gene sequence is then repeatedly reproduced and thus made visible.

The result of the analysis may only be opened by the attending physician and not by anyone else. At another appointment, the doctor explains the result of the analysis and a decision can be made as to whether further procedures are necessary.

Duration until the results arrive

The duration of the genetic test depends on the genetic material to be examined and the suspected disease.

Chromosome analyzes require less time than complex molecular genetic analyzes. With an average chromosome analysis, the working time amounts to approx. 10-20 working days.
Prenatal examinations are usually carried out more quickly. A chromosome analysis using sample tissue from the placenta can be carried out within a few days. Cells from the fruit cavity, on the other hand, must first artificially grow and mature, which can take between 2 and 3 weeks.

Molecular genetic examinations take different lengths of time, depending on the number of genes to be examined and the size of the gene sequences. These analyzes can take weeks to months.

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Risks

Medically, the risks of a genetic test are very low. In most cases, saliva or blood samples are sufficient for genetic analysis. A genetic test of the bone marrow cells is usually only carried out if the bone marrow aspiration would have been indicated anyway. Thus, medically, the very rare risks of injury or infection from the punctures remain.

However, evaluating the results of the genetic test can be risky. Before it is carried out, an informative discussion should take place with the doctor to explain the consequences and meanings of the genetic test.
The risk is that possible illnesses are not recognized and those affected feel a false sense of security. A negative result for a disease is no guarantee that you will not get sick. It can either be a false negative result or a spontaneous mutation that causes the disease.

On the other hand, it is possible that wrong results lead to emotional stress and intensive therapy, although there is no danger whatsoever. The risk of these incorrect evaluations and misinterpretations of the test results increases with commercial genetic tests that are carried out without the involvement of a doctor.

Evaluation of the sample

The sample is examined in a laboratory using a method that is appropriate to it. In principle, only what has been requested by the doctor is examined. You only get an answer to a specific question. The laboratory only determines whether the gene sequences sought are present in the cells of the person examined. A doctor must then evaluate what this means for the diagnosis, the disease and the subsequent therapy.

There is no complete analysis of the genome. This is because the capabilities of human genetics are still very much overestimated and empirical values ​​are not yet sufficient to reliably analyze such large quantities. It can happen that incorrect assignments are made due to the numerous small gene segments. The risk of errors therefore decreases with the targeted question. But it doesn't have to be this way forever. The genome analysis is becoming more and more precise and more and more sections are being decoded.

If a certain defective gene could be detected, e.g. if cystic fibrosis occurs, the diagnosis is clearly confirmed. Corresponding therapies may have to be initiated immediately. Predictive tests, such as the gene modification of the "BRCA" genes before the onset of cancer, can have different consequences. In addition to more stringent diagnostic procedures, preventive breast removals and radical therapy options are also offered for prevention. The decision is ultimately made by the patient.

Genetic test costs

Prices may vary depending on the test and provider. An average genetic test costs between 150 and 200 euros. However, the price can vary widely. As a rule, a test for hereditary cancer mutations costs at least 1000 euros, but should be covered by the health insurance company if there is evidence of a risk for an illness.

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Genetic tests from commercial providers that examine certain genetic characteristics can be available from as little as € 100. However, their informative value and reliability is not reliable, which is why such amateurish tests are not recommended.

The statutory health insurance pays a genetic test in full with appropriate justification. There are, however, exceptions that can be requested individually from the relevant cash register. This includes, above all, the tests for one's own interest, in which there is no risk factor or ancestry from different ethnic groups is to be determined. In the case of artificial insemination, a co-payment obligation can also be asserted under certain circumstances, so that the costs are not paid in full by the health insurance company.

Those who are privately insured are often reimbursed for “necessary medical treatment” depending on the insurance and individually agreed services. This is a broad term and can be requested at any time. In most cases, counseling sessions or various diagnostic examinations also fall within the scope of the “curative treatments”.

Does the health insurance company pay for my genetic test?

The assumption of costs by the health insurance company depends on the test carried out.
If, according to medical guidelines, there is a need for genetic diagnostics, which contribute to the investigation and treatment of the disease, the health insurers usually pay for this diagnostic procedure.

Depending on the insurance and entitlement, it is possible that individual services are not covered by the health insurance and have to be paid for privately. With some diseases or tumor markers, however, you can get help from associations and official networks for the relevant disease if the costs have been rejected by your own health insurance company. With just a few details about your own insurance and the reasons for the refusal to pay the costs, the costs can sometimes be paid through an association. However, it makes sense to inquire with the relevant health insurance company which services are covered before taking a test.

Breast Cancer - What Does BRCA Mean?

Breast cancer is a disease that is usually multifactorial. This means that many internal and external circumstances contribute to the coincidence of breast cancer development.
Angelina Jolie is one of the best-known examples of a genetic mutation that increases the risk of breast cancer. After the result that she had defects BRCA 1 and 2, she had her breasts and ovaries removed prophylactically.

About 5% of all breast cancer cases are hereditary, with a BRCA1 gene mutation in 40-50% and a BRCA2 gene mutation in 30-40%. These gene mutations increase their carriers' risk of developing breast cancer to around 50-80%. However, the mutations not only increase the likelihood of breast cancer, but colon cancer and ovarian cancer as well. Male carriers of the mutation not only increase the likelihood of breast cancer, but also of prostate cancer. However, it cannot be said with 100% certainty that cancer will actually occur. In the event of an abnormal genetic test, however, it is advisable to take advantage of the early cancer detection measures in order to discover a possible cancer in good time.

Women in particular, but men too, should have a genetic test performed if at least one or two breast and / or ovarian cancers have occurred in the family. Frequent risk factors are a long fertile time, dense glandular tissue of the breast, certain diet and behavior, as well as external circumstances such as the environment or the handling of certain substances. Intensive early detection through more stringent diagnostic procedures can significantly increase the prognosis and possible treatment opportunities in the event of breast cancer.

People with the following illnesses in their families should be tested:

  • 3 women with breast cancer

  • 2 women with ovarian cancer and / or breast cancer

  • 2 women with breast cancer, with at least one occurring under the age of 50

  • 1 man with breast cancer and 1 woman with breast or ovarian cancer

  • 1 woman with breast cancer and ovarian cancer

  • 1 woman under 50 years of age with breast cancer on both sides

  • 1 woman under 35 with breast cancer

For all further information please also read: The breast cancer gene, or BRCA mutation

Genetic test for colon cancer

Colon cancer is also favored by many influenceable internal and external influences and genetic constellations. Diet, behavior, and external circumstances play a significantly greater role in colon cancer than in breast cancer. Only about 5% of all colon cancers can be traced back to a genetic change.

If intestinal cancer and / or stomach cancer occur in close relatives at an early age (under 50 years of age) or if colon cancer and / or stomach cancer occur more frequently, this could be an indication to be tested. The tumor syndromes of hereditary non-polypoid colorectal carcinoma (HNPCC or Lynch's syndrome) and familial adenomatous polyposis (FAP) are the most common. The latter leads to the growth of many polyps at a young age, which can turn into tumors.

Colon cancer usually grows very slowly and can usually be removed at an early stage if it is discovered in good time. However, colon cancer often goes undetected because colon cancer screening is neglected and cancer often does not cause symptoms until the tumor has progressed. If you suspect a familial, hereditary component, you should seek medical advice and consider genetic testing. If the result is abnormal, regular preventive examinations should be carried out early on in order to find a cancer of the gastrointestinal tract early.

Read about this too: Is Colon Cancer Hereditary and Colon Cancer Screening

Prenatal diagnostics (PND) - genetic testing during pregnancy

The word prenatal diagnosis is made up of the components “pre” and “natal”, which means something like “before birth”. It is therefore a question of diagnostic measures for a pregnant woman to assess the condition of the child in the womb. There are intervening, i.e. invasive, and non-encroaching, i.e. non-invasive, methods. An important component here is ultrasound examinations, blood tests and sampling from the scarring or placenta. Diagnostics are used to identify malformations or diseases in the child. It can also be used to identify the father. In principle, not every disease can be clearly identified, but attempts are made to clarify certain diseases as safely as possible and, if necessary, to exclude them. An inconspicuous result does not necessarily rule out a disease or malformation.

In the event of abnormalities, however, this information can be very important in order to be able to treat a child in the womb. For example, in the case of fetal anemia, i.e. congenital anemia of the fetus, blood transfusions can be administered, which are very important for survival. Many other diseases can also be treated prenatally during pregnancy. The usefulness of a possible, planned, premature delivery can also be determined in this way.

Some changes in the chromosome distribution can also be detected in blood tests, as is the case with trisomies 13, 18 or 21, but also for example with Turner syndrome. Knowledge of such chromosomal abnormalities or malformations in the child can help with preparations and further life planning.

Determine parentage and origin

Descent is the range of relatives whose genetic makeup you carry.
Certain genes are located in different parts of the genome and can therefore be subject to different inheritance patterns. If there is a defective gene in the family history, it can therefore be calculated with what probability the following relatives have the genetic defect.

From a non-medical point of view, a genetic test for genealogy research can be carried out. However, it is important to know that the results are only based on probabilities and that certain gene characteristics are assigned to a country or ethnic group in which they occur most frequently. A genetic defect persists particularly in isolated populations of the same kind. For this reason, genetic diseases are present with very different frequencies in different regions of the world. One example of this is the so-called "beta-thalassemia", a hemoglobin disorder that occurs primarily in the central area.
However, this principle is quite imprecise and has caused misjudgments several times in the past. Most databases also contain more European characteristics, so that rare occurrences can usually not be correctly assigned.

Also read: Hereditary thalassemia

Another problem is that a person has more ancestors than gene segments and some genes can be lost during inheritance or simply cannot be passed on to the following generation. Although individual sequences can be filtered well in some cases, the exact assignment is almost impossible because the mixing of different ethnic groups has always been too much to be able to separate. It is believed that we all had the same ancestors 3,000-4,000 years ago, which makes it difficult to differentiate using genetic testing.

In principle, such genetic analyzes should be viewed critically. Humanity has spread over many different continents over the millennia and has often mixed up. Characteristics cannot therefore be clearly assigned to any ethnic group. However, due to the large mix of ethnicities, genetic tests are often used as an argument against racism. Since influences from other countries and tribes can be found in virtually everyone, xenophobia is nonsensical, so the reasoning.

Paternity test

One can not only try to decipher the ethnicity of other people, but also a fatherhood. If the samples from the child and (alleged) parents are compared, the child should have parts from both parents. If this is not the case and the child only has parts of the mother and parts of an indefinable person, this usually speaks for foreign paternity. If a child is genetically examined, the parents are often also examined automatically. For this reason, genetic diagnostics usually warn parents that testing the child's illnesses can reveal paternity.

Cystic fibrosis

Cystic fibrosis, or “cystic fibrosis”, is one of the best-known genetic diseases and, because of its consequences, it is very feared. The only cause is a pathological gene, which leads to a so-called “chloride channel” (CFTR channel) being incorrectly formed. As a result, highly viscous secretions form in numerous cells and organs of the body, which in particular can cause lung diseases, intestinal diseases and pancreatic complaints. The gene is inherited in a recessive manner, which means that the disease only occurs if both parents pass the pathological gene on to the child. In the case of pre-existing cases of illness in the family, parents can have themselves tested to determine whether they can carry the diseased gene and whether they can potentially pass it on to the child.

The different types of mutations can usually be found in a genetic test and allow a more precise statement about the severity of the disease. So it is a less severe case if the duct has poor conductivity than if it is not functional at all. These differences sometimes make a difference in treatment and can also provide an indication of life expectancy in the case of cystic fibrosis and pending transplants in the future. Even today with optimal therapy, the average life expectancy is only 40 years. The most common is a DeltaF508 mutation, in which there is a reduced number of channels and function is impaired.

You can find more information on this topic in our articles:

  • Life expectancy in cystic fibrosis
  • Symptoms of cystic fibrosis
  • Causes of cystic fibrosis

Lactose intolerance

A genetic test can only help to a limited extent in detecting lactose intolerance. The examination can very reliably diagnose a congenital, primary lactose intolerance in which the lactose-splitting enzyme called lactase is defective. However, a genetic test is not very effective in the case of lactose intolerance or secondary lactose intolerance. These clinical pictures arise, for example, from damage to the intestine, which can no longer adequately produce lactase. So there is no defect in the lactase gene that could be found in this way. Therefore, one should first fall back on conventional examination methods such as the H2 breath test. As a rule, however, the clinical symptoms and the improvement of symptoms when avoiding lactose are sufficient to establish a diagnosis.

More about this topic can be found:

  • Lactose intolerance
  • Symptoms of lactose intolerance

Can you detect rheumatism in a genetic test?

In rheumatology, too, genetic diagnostics are playing an increasingly important role, since increasing genetic characteristics are being researched as causal factors in certain rheumatic diseases. One of the best-known genetic traits that are frequently associated with rheumatic diseases is the "HLA B-27 gene". It is involved in the development of the diseases "Bechterew's disease", psoriasis, rheumatoid arthritis and numerous other diseases that are associated with rheumatological complaints.

However, for the vast majority of rheumatic diseases, several genetic defects or mutations are required for a disease to occur. Environmental factors also play an important role. Smoking or an unhealthy diet can have a huge impact here. A genetic test is therefore often indicated if a rheumatoid disease is suspected, but its informative value is rather poor in a (still) healthy person. Many people who do not get sick carry different genes at risk and the likelihood of actually getting sick is difficult to establish. In this case, genetic testing in advance is rarely effective. However, if it is a question of genetic diseases such as hemochromatosis, which often cause joint problems, a genetic test to confirm the disease makes perfect sense.

You can find everything else on the subject at: rheumatism

Hemochromatosis

Hemochromatosis is the most common genetic disease in Germany that is only triggered by a single genetic defect. Around every 400th person is affected.
The affected “HFE gene” suffers a single mutation that causes the intestine to absorb too much iron. Due to the significantly increased iron level in the blood and the limited possibilities for excretion, the iron is inevitably stored in cells and organs. The skin, joints, pancreas or liver are particularly affected. The latter can become seriously ill at an early age, which in the long term leads to cirrhosis of the liver and the need for a liver transplant.

Hereditary hemochromatosis is a hereditary disease that can be detected with certainty using genetic testing. If the diagnosis of sick people is too late, irreversible joint and organ damage may already have occurred. But just because you carry the pathological gene does not necessarily mean that the disease must break out. General screening for gene carriers is not yet the rule. The signs of hemochromatosis are joint discomfort and tiredness. If the blood test also reveals a problem in the iron balance, one should consider haemochromatosis and have it clarified.

Also read: Hemochromatosis or symptoms of hemochromatosis

Estimate the risk of thrombosis in a genetic test?

The development of the thrombosis is always multifactorial. Important influences on the development of a thrombosis are poor mobility, reduced blood flow in the veins, severe lack of fluids and an increased tendency to thrombosis due to different blood compositions.
Numerous components in the blood that lead to a tendency to thrombosis can be changed. This also includes genetic factors that lead to increased clotting in some people.
There are various congenital disorders of the blood coagulation system that greatly increase the risk of thrombosis. The testing of:

  • APC resistance (factor V Leiden mutation)
    The most common genetic disease with a tendency to thrombosis is APC resistance, which is triggered by a so-called “Factor V Leiden mutation”.

  • Prothrombin mutation

  • Antithrombin mutation

  • Mutation of protein C or S (e.g. protein S deficiency)

Anyone who suspects a hereditary disease should be clarified in case of familial accumulation or thromboses at a young age that recur or occur in atypical locations such as the arm.

Learn more at: How do I recognize a thrombosis

Alternatives to genetic testing

Depending on what exactly is to be tested, one can try to find alternative diagnostic methods for existing diseases in order to prove them. Unfortunately, there is no alternative to genetic testing if you want to find out whether you are at increased risk for a specific disease. For anything that would be a prediction, genetic testing would have to be carried out.
The other option would be to forego genetic testing. Despite family history or other risk factors, many people decide against a genetic test in order not to burden themselves psychologically with a possible diagnosis.

In general, it always makes sense to undergo preventive examinations in order to discover tumors or other diseases early on.


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