Rapid advances in DNA testing means that almost anyone can send their DNA for genetic testing at companies like 23andMe and Ancestry.com.  Genetic testing can be incredibly useful to understand more about your body and health – but what should you know before you order a DNA test?  DNA testing can reveal a lot about you and has some important strengths and limitations.  Here are the top 5 things to consider:

1. Not all genetic tests are made equally:

DNA testing can be divided into two primary groups, clinical testing and direct-to-consumer testing.  It is important to understand the differences because the uses and limitations of each test vary dependent on the type.

Clinical genetic testing: This is the type of testing that your doctor will order when you are in the hospital or making a visit to their office.  Clinical DNA testing is intended to provide a patient with a diagnosis for a genetic disease and can be quite expensive.  Clinical DNA testing is regulated by the government and is typically analyzed by doctors trained in Clinical Molecular Genetics.  This type of testing is used to make medical diagnoses and decisions.

Direct-to-consumer testing (DTC): Also called DTC, this type of testing can be run without the request of a doctor and is typically used for analysis of ethnicity or genealogy.  Recently some DTC tests have been approved by the FDA to return a small number of DNA variants that are associated with certain inherited diseases like cystic fibrosis.  Examples of a direct-to-consumer test include tests offered by 23andMe and Ancestry.com.

2. Think about your genetic privacy:

Privacy is perhaps the most important aspect of genetic testing that you should consider.  The information contained with your DNA is the blueprint for your body and is very valuable data.  Carefully consider the privacy implications before consenting to any genetic test.  In some cases, the value of the information provided by the DNA test may not be worth more than what you are giving away by providing your genetic material to a company!

Protecting your genetic privacy is particularly a concern in the case of Direct-to-Consumer (DTC) tests where some companies are actually more interested in acquiring and analyzing your genetic material than they are in providing you with insights about your DNA.  Know that your DNA has even more value when it is linked to other information about you – especially your lifestyle, habits and healthcare information.  If you consent to research, the Direct-to-consumer companies may look for correlations and associations between DNA changes and certain behaviors – these connections can be harvested for additional research and sold to drug companies.  This type of research is potentially scientifically useful because it enables scientists to understand more about our DNA, but you should be very aware about how any information that you provide might be used.

3. Consider the expense of the test:

The cost of a DNA test is dependent on the technology being used.  A clinical genetics test can range in price from $200 to $10,000 dollars depending on the type of test and the complexity of the analysis.  Direct-to-consumer testing for ancestry, genealogy and health information ranges in cost from $69.00 to $199 dependent on the company you use.  Paternity test kits can be ordered for approximately $70.00 – but make sure the test is accepted by courts if this is the intended use for the results.

4. Understand that the results of DNA testing can reveal a lot about you and your family:

Here are some examples of what a DNA test kit might reveal:

Your ethnicity and ancestry: At home DNA test kits like AncestryDNA and 23andMe use DNA genotyping to profile the ancestral composition of a person’s DNA.  These test kits may reveal results that agree with what a person already knows or may reveal unexpected results about a person’s genetic makeup, such as the presence or absence of specific ethnicities in their DNA.

You might be a carrier for a genetic disease: Direct-to-consumer test kits can use DNA genotyping to check whether a person is a carrier for specific DNA changes associated with some genetic conditions.   It is very important to understand that the direct-to-consumer DNA tests are *not comprehensive* which means that they do not test for all possible DNA changes that might make you a carrier.  This means that a negative test report is possible even if you are a carrier.  If you are concerned about your carrier status for a genetic condition, consult your doctor for a referral to clinical genetic testing.

The possibility of genetic risks: In some cases, a direct-to-consumer test may return results that indicate an altered risk for a certain health condition.  These types of risk calculations attempt to use DNA genotyping to find associations between a person’s DNA and certain traits or behaviors.  The test may indicate an increased or decreased risk for a particular condition.  The company is basing this prediction of ‘risk’ based on an association of the DNA change with a specific trait.  This means that a researcher found that people with trait were more likely or less likely to have the DNA change than expected.  A genetic risk does not guarantee you will exhibit a trait.

Non-paternity of a relative: Some direct-to-consumer tests are paternity tests that look for how much DNA is shared between two people.  Understandably, these tests may report that a person who is thought to be the biological father of a child is not genetically related to the child.

5. Understand the limitations of the DNA test kit:

Most direct-to-consumer DNA tests are not comprehensive: DNA genotyping tests like those offered by 23andMe and Ancestry.com rely upon a technology that only looks at some but not all DNA changes. This means that a ‘negative’ result for one of these tests might not be truly negative because a DNA change that isn’t being tested for could be present in your genome.   Always consult a health care provider if you are concerned about a genetic condition.

Direct-to-consumer DNA tests are not designed or intended for making medical decisions: Direct to consumer tests have utility and educational value but are not intended to provide information that is used for medical decisions.  The FDA currently limits direct-to-consumer companies from making many claims or providing significant health information from at-home tests.  There are limited exceptions to this rule.

Direct-to-consumer tests provide ‘trait’ associations: The wellness and trait associations generated by at-home test kits are associations that are not guarantees of a trait or that a prediction generated by the test will come true.  Consider the utility of what a slightly changed probability for a given trait would mean to you prior to ordering the test.  Because the DNA code is so complicated, it can be very difficult to determine what the impact of a DNA variant will be (see the post on “What is DNA” for more details on different DNA variant types that genetic testing can find).

Direct-to-consumer companies may use your DNA for research by other companies: Some direct-to-consumer DNA testing companies may ask that you opt-in to research that enables them to look for associations between your genome and other information that you provide.  These companies may also perform additional DNA testing on your DNA sample if allowed.  If you opt-in, a company that you send your DNA to might sell this information to other companies or ask that you participate in additional studies based upon your genetic information.  Carefully consider the implications of providing your DNA to a company and make sure you are providing informed consent.

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Drew Michael, Ph.D.
Dr. Drew Michael is a Clinical Molecular Geneticist and Clinical Biochemical Genetics fellow. He holds a Ph.D. in Molecular Cell Biology and an M.S. in Biochemistry and Molecular Biology. Dr. Michael has an extensive background in molecular and computational genomics and runs a research program designed to understand the gene regulatory programs which control human development and disease. His diagnostic research is focused on the molecular and biochemical diagnosis of rare human diseases. Outside of science and medicine, he really likes dogs and lives in Washington, D.C. with two german shepherds.