Genetic testing


Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or through biochemical analysis to measure specific protein output. In a medical setting, genetic testing can be used to diagnose or rule out suspected genetic disorders, predict risks for specific conditions, or gain information that can be used to customize medical treatments based on an individual's genetic makeup. Genetic testing can also be used to determine biological relatives, such as a child's parentage through DNA paternity testing, or be used to broadly predict an individual's ancestry. Genetic testing of plants and animals can be used for similar reasons as in humans, to gain information used for selective breeding, or for efforts to boost genetic diversity in endangered populations.
The variety of genetic tests has expanded throughout the years. Early forms of genetic testing which began in the 1950s involved counting the number of chromosomes per cell. Deviations from the expected number of chromosomes could lead to a diagnosis of certain genetic conditions such as trisomy 21 or monosomy X. In the 1970s, a method to stain specific regions of chromosomes, called chromosome banding, was developed that allowed more detailed analysis of chromosome structure and diagnosis of genetic disorders that involved large structural rearrangements. In addition to analyzing whole chromosomes, genetic testing has expanded to include the fields of molecular genetics and genomics which can identify changes at the level of individual genes, parts of genes, or even single nucleotide "letters" of DNA sequence. According to the National Institutes of Health, there are tests available for more than 2,000 genetic conditions, and one study estimated that as of 2017 there were more than 75,000 genetic tests on the market.

Types

Genetic testing is "the analysis of chromosomes, proteins, and certain metabolites in order to detect heritable disease-related genotypes, mutations, phenotypes, or karyotypes for clinical purposes." It can provide information about a person's genes and chromosomes throughout life.
There are a number of types of testing available, including:
Non-diagnostic testing includes:
Genetic testing is often done as part of a genetic consultation and as of mid-2008 there were more than 1,200 clinically applicable genetic tests available. Once a person decides to proceed with genetic testing, a medical geneticist, genetic counselor, primary care doctor, or specialist can order the test after obtaining informed consent.
Genetic tests are performed on a sample of blood, hair, skin, amniotic fluid, or other tissue. For example, a medical procedure called a buccal smear uses a small brush or cotton swab to collect a sample of cells from the inside surface of the cheek. Alternatively, a small amount of saline mouthwash may be swished in the mouth to collect the cells. The sample is sent to a laboratory where technicians look for specific changes in chromosomes, DNA, or proteins, depending on the suspected disorders, often using DNA sequencing. The laboratory reports the test results in writing to a person's doctor or genetic counselor.
Routine newborn screening tests are done on a small blood sample obtained by pricking the baby's heel with a lancet.

Risks and limitations

The physical risks associated with most genetic tests are very small, particularly for those tests that require only a blood sample or buccal smear. The procedures used for prenatal testing carry a small but non-negligible risk of losing the pregnancy because they require a sample of amniotic fluid or tissue from around the fetus.
Many of the risks associated with genetic testing involve the emotional, social, or financial consequences of the test results. People may feel angry, depressed, anxious, or guilty about their results. The potential negative impact of genetic testing has led to an increasing recognition of a "right not to know". In some cases, genetic testing creates tension within a family because the results can reveal information about other family members in addition to the person who is tested. The possibility of genetic discrimination in employment or insurance is also a concern. Some individuals avoid genetic testing out of fear it will affect their ability to purchase insurance or find a job. Health insurers do not currently require applicants for coverage to undergo genetic testing, and when insurers encounter genetic information, it is subject to the same confidentiality protections as any other sensitive health information. In the United States, the use of genetic information is governed by the Genetic Information Nondiscrimination Act .
Genetic testing can provide only limited information about an inherited condition. The test often can't determine if a person will show symptoms of a disorder, how severe the symptoms will be, or whether the disorder will progress over time. Another major limitation is the lack of treatment strategies for many genetic disorders once they are diagnosed.
Another limitation to genetic testing for a hereditary linked cancer, is the variants of unknown clinical significance. Because the human genome has over 22,000 genes, there are 3.5 million variants in the average person's genome. These variants of unknown clinical significance means there is a change in the DNA sequence, however the increase for cancer is unclear because it is unknown if the change affects the gene's function.
A genetics professional can explain in detail the benefits, risks, and limitations of a particular test. It is important that any person who is considering genetic testing understand and weigh these factors before making a decision.
Other risks include incidental findings—a discovery of some possible problem found while looking for something else. In 2013 the American College of Medical Genetics and Genomics that certain genes always be included any time a genomic sequencing was done, and that labs should report the results.

Direct-to-consumer genetic testing

genetic testing is a type of genetic test that is accessible directly to the consumer without having to go through a health care professional. Usually, to obtain a genetic test, health care professionals such as physicians, nurse practitioners, or genetic counselors acquire their patient's permission and then order the desired test, which may or may not be covered by health insurance. DTC genetic tests, however, allow consumers to bypass this process and purchase DNA tests themselves. DTC genetic testing can entail primarily genealogical/ancestry-related information, health and trait-related information, or both.
There is a variety of DTC tests, ranging from tests for breast cancer alleles to mutations linked to cystic fibrosis. Possible benefits of DTC testing are the accessibility of tests to consumers, promotion of proactive healthcare, and the privacy of genetic information. Possible additional risks of DTC testing are the lack of governmental regulation, the potential misinterpretation of genetic information, issues related to testing minors, privacy of data, and downstream expenses for the public health care system. In the United States, most DTC genetic test kits are not reviewed by the Food and Drug Administration, with the exception of a few tests offered by the company 23andMe. As of 2019, the tests that have received marketing authorization by the FDA include 23andMe's genetic health risk reports for select variants of BRCA1/BRCA2, pharmacogenetic reports that test for selected variants associated with metabolism of certain pharmaceutical compounds, a carrier screening test for Bloom syndrome, and genetic health risk reports for a handful of other medical conditions, such as celiac disease and late-onset Alzheimer's.

Controversy

DTC genetic testing has been controversial due to outspoken opposition within the medical community. Critics of DTC testing argue against the risks involved, the unregulated advertising and marketing claims, the potential reselling of genetic data to third parties, and the overall lack of governmental oversight.
DTC testing involves many of the same risks associated with any genetic test. One of the more obvious and dangerous of these is the possibility of misreading of test results. Without professional guidance, consumers can potentially misinterpret genetic information, causing them to be deluded about their personal health.
Some advertising for DTC genetic testing has been criticized as conveying an exaggerated and inaccurate message about the connection between genetic information and disease risk, utilizing emotions as a selling factor. An advertisement for a BRCA-predictive genetic test for breast cancer stated: “There is no stronger antidote for fear than information.” Apart from rare diseases that are directly caused by specific, single-gene mutation, diseases "have complicated, multiple genetic links that interact strongly with personal environment, lifestyle, and behavior."
Ancestry.com, a company providing DTC DNA tests for genealogy purposes, has reportedly allowed the warrantless search of their database by police investigating a murder. The warrantless search led to a search warrant to force the gathering of a DNA sample from a New Orleans filmmaker; however he turned out not to be a match for the suspected killer.

Governmental genetic testing

In Estonia

As part of its healthcare system, Estonia is offering all of its residents genome-wide genotyping. This will be translated into personalized reports for use in everyday medical practice via the national e-health portal.
The aim is to minimise health problems by warning participants most at risk of conditions such as cardiovascular disease and diabetes. It is also hoped that participants who are given early warnings will adopt healthier lifestyles or take preventative drugs.

Government regulation

In the United States

With regard to genetic testing and information in general, legislation in the United States called the Genetic Information Nondiscrimination Act prohibits group health plans and health insurers from denying coverage to a healthy individual or charging that person higher premiums based solely on a genetic predisposition to developing a disease in the future. The legislation also bars employers from using individuals’ genetic information when making hiring, firing, job placement, or promotion decisions. The legislation, the first of its kind in the United States, was passed by the United States Senate on April 24, 2008, on a vote of 95–0, and was signed into law by President George W. Bush on May 21, 2008. It went into effect on November 21, 2009.
In June 2013 the US Supreme Court issued two rulings on human genetics. The Court struck down patents on human genes, opening up competition in the field of genetic testing. The Supreme Court also ruled that police were allowed to collect DNA from people arrested for serious offenses.

In popular culture

Some possible future ethical problems of genetic testing were considered in the science fiction film Gattaca, the novel Next, and the science fiction anime series "Gundam Seed". Also, some films which include the topic of genetic testing include The Island, , and the Resident Evil series.

Ethics

Pediatric genetic testing

The American Academy of Pediatrics and the American College of Medical Genetics have provided new guidelines for the ethical issue of pediatrics genetic testing and screening of children in the United States. Their guidelines state that performing pediatric genetic testing should be in the best interest of the child. In hypothetical situations for adults getting genetically tested 84-98% expressing interest in getting genetically tested for cancer predisposition. Though only half who are at risk of would get tested. AAP and ACMG recommend holding off on genetic testing for late-onset conditions until adulthood. Unless diagnosing genetic disorders during childhood and start early intervention can reduce morbidity or mortality. They also state that with parents or guardians permission testing for asymptomatic children who are at risk of childhood onset conditions are ideal reasons for pediatrics genetic testing. Testing for pharmacogenetics and newborn screening is found to be acceptable by AAP and ACMG guidelines.
Histocompatibility testing guideline states that it's permissible for children of all ages to have tissue compatibility testing for immediate family members but only after the psychosocial, emotional and physical implications has been explored. With a donor advocate or similar mechanism should be in place to protect the minors from coercion and to safeguard the interest of said minor.
Both AAP and ACMG discourage the use of direct-to-consumer and home kit genetic because of the accuracy, interpretation and oversight of test content.
Guidelines also state that if parents or guardians should be encouraged to inform their child of the results from the genetic test if the minor is of appropriate age. If minor is of mature appropriate age and request results, the request should be honored. Though for ethical and legal reasons health care providers should be cautions in providing minors with predictive genetic testing without the involvement of parents or guardians. Within the guidelines AAP and ACMG state that health care provider have an obligation to inform parents or guardians on the implication of test results. To encourage patients and families to share information and even offer help in explain results to extend family or refer them to genetic counseling.
AAP and ACMG state any type of predictive genetic testing for all types is best offer with genetic counseling being offer by Clinical genetics, genetic counselors or health care providers.

Israel

Israel uses DNA testing to determine if people are eligible for immigration. The policy where "many Jews from the Former Soviet Union are asked to provide DNA confirmation of their Jewish heritage in the form of paternity tests in order to immigrate as Jews and become citizens under Israel's Law of Return" has generated controversy.

Costs

The cost of genetic testing can range from under $100 to more than $2,000. This depends on the complexity of the test. The cost will increase if more than one test is necessary or if multiple family members are getting tested to obtain additional results. Costs can vary by state and some states cover part of the total cost.
From the date that a sample is taken, results may take weeks to months, depending upon the complexity and extent of the tests being performed. Results for prenatal testing are usually available more quickly because time is an important consideration in making decisions about a pregnancy. Prior to the testing, the doctor or genetic counselor who is requesting a particular test can provide specific information about the cost and time frame associated with that test.