… but how can healthcare professionals make sure they are equipped to support patients who are worried and distressed about their results?
Personalised – or direct-to-consumer – DNA testing is becoming more popular, and around Christmas you may have seen brands such as 23andMe and AncestryDNA promoting their testing kits as gifts. Processing of these kits takes around 6-8 weeks so, this month, recipients who were quick to send theirs off can expect to receive their results.
Many of these kits focus on ancestry only, but some also offer a health option, which can include screening for known gene variants linked to various conditions. The results always come with a disclaimer to the effect that if the customer is confused or concerned about any of their results, they should contact their GP.
What does the test do?
23andMe states its health test is not diagnostic, and therefore does not test for single-gene diseases. Instead, it tests for gene variants associated with increased risk of several conditions, including Parkinson’s and Alzheimer’s. In both conditions, causation is still poorly understood but is known to involve both genetic and environmental factors.
A person finding out that they have an increased risk of developing such a condition will likely experience some degree of alarm and distress. Health professionals may encounter patients in this situation, which can present a challenge – especially if they are unfamiliar with the nature of these genetic tests.
23andMe also offers carrier status information for a list of conditions, ranging from Tay-Sachs and cystic fibrosis to hereditary fructose intolerance. These are all autosomal recessive conditions, some of which are considered serious enough to warrant the use of pre-implantation genetic diagnosis to avoid passing them on.
As well as causing concern among patients hoping to start a family, this information may be distressing to those who are already parents who worry that their existing children are affected. As a result, it may not be just the people who take the test who then go on to seek medical advice. It can be expected that relatives of individuals who have found out that they have disease-causing or high-risk variants may come forwards seeking testing.
Not the whole picture
It is important to note that companies such as AncestryDNA and 23andMe are not offering whole genome sequencing. Their tests are based on genotyping, which looks for specific variants, rather than all of a person’s genetic information. It is not clear whether consumers are generally aware of the difference.
Patients may also be unaware of how many genes can influence the risk of getting a particular condition. For example, the BRCA genes are well known, but there are over 70 other gene variants associated with breast cancer. Individually none affect risk as significantly as the BRCA genes, but cumulatively they can have a huge effect.
The concern is that a patient who has been tested for a couple of variants associated with a particular disease may assume that their risk is low (or high if the result was positive), when in fact there are numerous other genetic and environmental factors that they are not taking account of.
Even if a patient has had their whole genome privately sequenced, the interpretive information they receive with their results is unlikely to go into detail about 70+ genes for each one among hundreds of diseases, so the estimates for risk for conditions such as cancers or cardiovascular disease may be deceptive.
Ultimately, it is important for health professionals to be aware of the nature of these direct-to-consumer genetic tests in order to be able to put the results in context for their patient, as well as to recognise where referral to clinical genetics may be appropriate.