What GPs need to know about the rising popularity of personal genomic testing

The RACGP’s recently published guide, Genomics in General Practice, warns that the current ‘clinical utility’ of personal genomic testing (PGT) is variable – and an unexpected answer could cause personal problems or even impact a patient’s life insurance premiums.
 
Associate Professor Grant Blashki from the Nossal Institute for Global Health at Melbourne University was on the guide’s advisory group. He told newsGP that PGT is being actively marketed to patients for reasons such as identifying possible future genetic diseases, carrier screening, and even fitness or sporting abilities.
 
‘Personal genomic testing requires that the patient has thought carefully about the implications of the test,’ he said. ‘The nature of the genetic tests varies widely, with vastly different implications and costs to the patient.’
 
Associate Professor Blashki believes GPs are ideally placed to help dispel common myths and boost genetic literacy in the community.
 
‘Many patients think if they have a gene that they will definitely get a disease, and if they don’t have the gene they and their family can never get the disease – neither of which is true,’ he said.
 
Associate Professor Blashki said GPs could play a vital role helping patients understand the evidence base for PGT, including developing a ‘healthy scepticism about extravagant claims’.
 
He said the most useful tests were those offering strong predictions of risk, such as the BRCA1 gene for familial breast and ovarian cancer. There were also limited predictors of disease – for example, APO-ε4 for Alzheimer’s disease. Some patients might find it useful to know their carrier status for recessive conditions such as cystic fibrosis, or to identify gene variants that affect how drugs impact them.
 
‘It is important in advance that patients consider who is going to be assisting with interpretation once the tests are done,’ Associate Professor Blashki said.
 
‘Some companies offer genetic counsellors who provide well-informed evidence-based interpretation, whilst others just provide the test information without elucidation.’
 
Associate Professor Blashki said a lack of professional assistance offered by the PGT company was a red flag, a warning backed by a recent article in The Conversation around risks of DNA testing.
 
In a recent book chapter on the topic published with Professor Jon Emery, who also advised on the RACGP’s genomics guide, Associate Professor Blashki observes that PGT has the potential to ‘cause patient distress [and] to identify issues that may have implications for the broader family’.
 
It was important to talk about a patient’s reasons for seeking the tests. Some might be seeking to screen for particular conditions, others might be curious, while a third group might be hoping to boost their wellness. 
 
Associate Professor Blashki said there was more evidence needed for some genomic wellness tests claiming to inform tailored fitness and nutrition regimens, with a good deal of uncertainty around testing for complex diseases like diabetes.
 
The RACGP’s guide gives the example of the increasingly popular test for MTHFR gene variants. Many patients now seek this test out, perhaps due to complementary or alternative medicine practitioners who recommend it as a way to investigate infertility or miscarriage. However, the guide states that there is presently ‘no substantial evidence’ to support the test, and that knowledge of the gene variants is unlikely to change patient management.
 
In addition, Associate Professor Blashki warns that there may be unexpected costs involved of discovering genetic risks.
 
‘GPs can advise patients that they should consider the insurance implications of PGT, especially if they are hoping to apply for new disability or life insurance. In which case, they are required to disclose “every matter known to the applicant, or could reasonably be expected to be known, that is relevant to the insurer’s decision”, which includes genetic tests,’ he said.

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