Genetics and stem cells

New rules for home DNA tests

New guidelines on commercial genetic testing may stop “customers being given wrong information about their health”, says The Guardian. Manufacturers of home genetic test kits, which are often sold from abroad over the internet, claim they can predict the risk of illnesses such as cancer or Alzheimer’s disease.

However, experts are concerned about many aspects of these tests, including their scientific validity and accuracy. There are also concerns that consumers who buy test kits may not fully understand the implications or the results, and may receive little guidance either before or after taking them.

The new voluntary guidelines, published by the UK’s Human Genetics Commission, recommend basic standards for companies selling the tests, which scan the DNA found in blood or mouth swabs. These standards should include the offer of counselling on genetic testing for diseases, as well as the provision of independent evidence for the tests and the secure storage of genetic information.

What are home genetic tests?

Genetic tests scan the genetic code of a person’s DNA to identify abnormalities, mutations or variations that may have medical implications, such as detecting particular genes that can raise the risk of cancer. Most of the time, this type of testing is used to detect genetic variations that are associated with inherited disorders.

When performed correctly, a genetic test can confirm or rule out some genetic conditions or help to determine a person’s chance of passing on a genetic disorder. They can also identify genetic sequences associated with a higher risk of developing a specific condition, although they cannot confirm that a person will definitely go on to develop that illness. Several hundred genetic tests are currently in use, with more being developed.

In the past, genetic testing was only available through doctors or genetic counsellors, but more recently home testing kits have been marketed directly to consumers via the internet and magazine adverts. These genetic tests usually involve the collection of a DNA sample at home, through either a blood sample or a swab from the inside of the cheek. The sample is then mailed back to the laboratory for analysis and consumers can be told the results (such as their likelihood of developing a certain disease), by mail or telephone, or online.

What conditions do they test for?

A person’s genetic code may influence the risk of particular diseases in several different ways. For example:

  • Some diseases, such as Huntingdon’s disease, is caused by the presence of a single, “dominant” gene. These are known as “autosomal dominant single-gene disorders”.
  • Some diseases, such as cystic fibrosis, will only develop if a person has two copies of a mutant gene (one inherited from each parent).
  • The code found in some sections of DNA may be associated with a slightly increased risk of developing a disease, with a number of fragments contributing to a person’s overall risk of a disease.
  • Even if a person does not have a particular disease, they may be carriers of genes that can affect their child’s risk of a particular disease. For example, two parents may each carry only a single cystic fibrosis gene that leaves them unaffected but means their children may develop the disease.

Several different types of genetic tests are available, and their manufacturers claim the tests can:

  • Predict the chance of developing inherited diseases, for example, genetic testing for the BRCA1 and BRCA2 gene mutations, which can cause breast cancer.
  • Test for certain genetic disorders that will develop if one copy of a gene is present.
  • Identify or rule out whether a person’s symptoms are caused by a specific medical condition.
  • Identify if a person is a carrier of a condition. This means that although they are not themselves affected, there is a risk their children may be affected.
  • Indicate a person’s genetic susceptibility to conditions as they age, such as Alzheimer’s or age-related macular degeneration.
  • Act as “nutrigenetic” tests, which some claim can provide information about how an individual’s health is affected by a particular nutrient or diet.

It is important to note that in most cases, genetic testing alone cannot tell people their likelihood of developing a disease. Most diseases occur as a result of interaction between genes, lifestyle factors (such as diet, the amount of exercise performed and whether someone smokes or drinks, for example), as a consequence of other diseases or conditions (e.g. diabetes causing high blood pressure), and even environmental factors. In the majority of cases, genetic testing, even when carried out to high standards, is only one piece of information about susceptibility to disease.

Genetic testing is also a relatively young technique, meaning that we are constantly finding new associations between genetics and certain diseases and are likely to find them for years to come. As our knowledge in this fledgling area of science is incomplete, it means that the results of today’s genetic tests are limited by what we have yet to discover.

What guidelines have been proposed?

The new guidelines have been developed by the UK Human Genetics Commission, which is the Government’s advisory body on developments in human genetics and their ethical, legal, social and economic implications. The commission’s new set of guidelines, “A common framework of principles for direct-to-consumer genetic testing services”, covers all aspects of direct-to-consumer genetic testing, including marketing, the provision of information and support to consumers, consent and data protection and laboratory analysis. The chief recommendations are as follows:

  • Consumers should be made aware of possible outcomes of taking a test, such as what they can expect to find out and what to do about the results.
  • Tests for serious hereditary diseases such as Huntingdon’s and breast cancer should only be provided with the offer of counselling both before and after testing.
  • Consumers should be provided with easy-to-understand information on how genetic testing works and what the results mean.
  • Any claims made about tests should be supported by evidence published in scientific journals.
  • Companies should be clear about the limitations of such tests and provide consumers with information about other factors that might play a role, such as lifestyle.
  • DNA samples and genetic information should be kept secure and companies should ensure that those being tested have provided consent.
  • Tests should be carried out by accredited laboratories that have appropriate quality-assurance procedures in place.

Why have the recommendations been made?

The voluntary guidelines have been published because of growing concern about many aspects of DIY genetic testing. These include anxieties about whether consumers are given enough information or counselling about genetic testing, whether the tests themselves are supported by scientific evidence, and whether the sensitive genetic information being gathered could be used or passed on for other purposes.

Genetic test kits bought in the UK are often marketed and analysed abroad and are therefore subject to foreign genetic and medical regulation. For example, a number of larger testing companies are based in the US, where there are few regulations over the use of genetic testing. The Human Genome Project, a scientific leader in genetic analysis, considers this lack of regulation to be problematic:

“Currently in the United States, no regulations are in place for evaluating the accuracy and reliability of genetic testing. Most genetic tests developed by laboratories are categorised as services, which the Food and Drug Administration (FDA) does not regulate.

“This lack of government oversight is particularly troublesome in light of the fact that a handful of companies have started marketing test kits directly to the public. Some of these companies make dubious claims about how the kits not only test for disease but also serve as tools for customising medicine, vitamins and foods to each individual's genetic make-up.”

If I want to be tested /screened what should I do?

Genetic testing can have both benefits and drawbacks, and the decision about whether to be tested is very personal. It is best in the first instance to talk to your doctor or a genetic counsellor if you have concerns about your possible genetic susceptibility to a particular disease, to see whether genetic testing is the right approach and whether it could provide useful information for you.

If you are considering a home test, give careful consideration to the benefits compared to the limitations and possible implications of the test, including psychological effects. Most importantly, ensure that the test and the test provider adhere to the principles of the new guidelines outlined here. Always discuss the results with your doctor before making any decisions about health care or treatment.

NHS Attribution