In a genetic test, the genetic material of a human is examined, usually to estimate the risk of a disease, to determine the exact cause of cell changes or hereditary conditions. For the examination, a blood sample or a small amount of saliva is usually used. So far, genetic tests only make sense for a few diseases. Because the results of the genetic analysis can affect the employment or insurance relationship, but also children and siblings, they may only take place in certain circumstances. This is regulated in Germany in its law, the Gene Diagnostics Act.
What types of genetic tests are there?
Depending on the significance of the result, three different types of genetic tests can be distinguished:
Diagnostic genetic tests: Your main task is to find the cause of an already existing disease.
Predictive genetic tests: They are used to identify specific characteristics of a person, such as the effect of a drug, or that, together with environmental factors, can trigger the disease. Predictive genetic testing can help plan treatment.
Prognostic genetic tests: These can predict the risk of future diseases. They can also tell you how likely it is to pass on a genetic trait or illness to your children.
Genetic tests are not only possible for medical questions. They are used, for example, in research, but also in law enforcement or to clarify the descent, such as in a paternity test.
How is the examination performed?
The genetic information is located in the nucleus of a body cell on the chromosomes. These consist of ladder-shaped DNA strands, the actual carriers of genetic information. That’s why a genetic test is called DNA analysis. Genes are single sections of a DNA strand.
As a rule, cells from the blood are examined for a genetic test. A standard blood sample is sufficient for this. Sometimes hair or cells from the oral mucosa are also considered. All it takes is to take an example from the inside of the buccal mucosa using a cotton swab.
The genetic material is then isolated from the cells, and the sequence of chemical “letters” from which all genes are constructed is read with exact procedures. By comparing the series of letters, different genes and changes in a gene can be accurately identified.
The analysis is carried out by a licensed laboratory. It can take several weeks for the result to be known.
What significance does a genetic change have?
Genes can have many functions. Mostly in a gene is the blueprint for a specific protein (protein). Each protein has a particular role; it controls, for example, part of the metabolism or is involved in cell division. If a gene is altered, “protein” may be so changed that it no longer functions properly and, for example, confuses the metabolism. Other gene modifications make sure that a cell produces a protein that is not intended. Since proteins have very different tasks, it depends on the exact change, what it means for health.
When a protein is completely lacking due to a genetic defect, the effects are often quite noticeable: There are several thousand hereditary diseases that are based on the fact that a gene change leads to the breakdown of a protein.
Other gene modifications are of little importance to health. The effects often depend on other genes and lifestyle and environmental factors. This is one reason why even genetic tests only allow safe predictions about health in exceptional cases and often do not say more than regular examinations.
What are genetic tests for?
For example, genetic research can help answer the following questions:
What is the cause of a disease and how can it be treated?
Genetic studies are used, for example, in some cancers to show which genomic mutations are responsible for a tumor. As a result, cancer cells can sometimes be better targeted. For example, this special treatment is available for breast, lung, colon and skin cancers, but only in a small proportion of patients.
For some infectious diseases, such as hepatitis C, the pathogen can also be tested using genetic tests. Certain types of hepatitis C virus are more accessible to treat than others.
A genetic test can also give indications as to whether a drug is tolerated and has sufficient effect.
Are there certain disease risks?
If a family has a high prevalence of a disease, it may indicate hereditary susceptibility. In such cases, a genetic test may be considered: He can then investigate which gene variant a person and perhaps his relatives own. Such genetic tests exist, for example, for hereditary diseases such as cystic fibrosis or the disorder of the chorea Huntington.
Genetic testing can also take place before the birth of a child (prenatal genetic testing). However, they are only permitted to detect genetic changes that may affect the child’s health before or after birth. Genetic tests for diseases that occur after the age of 18 are prohibited before birth.
How and when is a genetic test advised?
Genetic investigations are regulated in Germany in the gene diagnostics law. It determines when which examinations are allowed and which information is obligatory. The Genetic Diagnostics Act also stipulates that no genetic survey may take place without the express written consent of the person concerned.
When educating, the doctor must inform about the procedure, the risks and the possible consequences of the test. There is a reasonable amount of time between the interview and the examination. Important: There is also a right not to know.
In addition to education, the Gene Diagnostics Act provides for specific genetic counseling on the potential medical, psychological and social effects of a genetic test – for example, if the analysis has identified a risk of an incurable disease. When such counseling sessions have to be offered depends on the nature of the genetic examination. In some genetic tests (for example, before birth) counseling is provided before the trial, in others only when the test result is present.
The advice should be understandable, leave open the decision on the further course of action and also call out contact points, which can assist with physical or mental stress. Human genetic counseling offers many practices that also perform a genetic test. According to the Genetic Diagnostics Act, only specialists in human genetics or with a similar additional qualification may conduct the consultation.
What are the risks of a genetic test?
Like all examinations, genetic examinations have only limited validity. Most not all, but only the most common gene changes are discovered. Even if an altered gene is found, it can often not be reliably predicted whether and when a disease breaks out in a human being. Conversely, even an inconspicuous (negative) test result does not give one hundred percent certainty that you will not get sick.
Although the risk of diseases such as diabetes, asthma, high blood pressure or coronary heart disease may be hereditary, it usually depends on environmental conditions and personal lifestyle. Therefore, genetic tests are generally not very meaningful in these diseases.
The knowledge of an increased risk or heredity for a disease that can not be treated or cured is distressing and can cause many fears. This applies, for example, to hereditary forms of Alzheimer’s dementia or the neurological disorder Huntington’s disease.