Gene testing for the public—a way to ward off disease, or a useless worry?

June 22, 2017 by David Amor, The Conversation
If you were destined for dementia in your 60s, but there was nothing you could do about it, would you want to know? Credit: shutterstock.com

The launch in Australia of a genomic testing service aimed at healthy people heralds a new era of individual patient care. A scan of your genome, which is the complete set of your genes, to find out if you are at risk of particular diseases, can mean you can then go on to take preventive measures against them.

The CEO of the Garvan Institute's Genome.One lab, which is offering the testing, said it would transform the health system, making it more focused on prevention than treatment of disease.

Genomic testing can have tremendous benefits, as in the case of diagnosing children with rare diseases. When applied to the right patients, can provide a diagnosis for more than half of patients with unusual symptoms. And the cost of this to the health system is much lower than for traditional diagnostic tests.

Certainly that all sounds like a good thing, but genomic testing is not yet the precision diagnostic and treatment tool we hope it will one day be. And all genetic knowledge is not necessarily helpful. As with any medical intervention, genomic testing carries risks as well as benefits.

Why genomic testing?

Genomic testing takes advantage of recent advances in our knowledge of genetic causes of disease, as well as technology. It's a of all 23,000 genes in the body at once.

The success of genomic testing in diagnosing rare disorders has raised the question of whether these tests should be performed in before they become sick. The potential benefits of testing healthy people are obvious, especially when it comes to conditions that have a proven treatment or prevention.

Cancer is a good example of where genomic testing can save lives. A person found to carry a genetic predisposition to bowel cancer can choose to have regular colonoscopies, which can detect and remove pre-cancerous growths before they cause harm.

And because genetic disorders run in families, potential health benefits can extend to other family members who may have the same genetic predisposition.

The ultimate goal of genomic testing, as part of personalised medicine, is that it will be available to everyone, allowing each person's health care to be tailored to their individual genetic make-up. In the future, this "lifetime health resource" promises to improve health care from conception to death.

Are we ready for this?

A considerable challenge of genomic testing is the extraordinary complexity of each person's genome. To try to interpret a single human genome is to grapple with literally millions of genetic variants, or points where the person's genetic code differs from the average person's.

Perhaps a handful of these variants will cause disease, but the rest will most likely be harmless. Determining which is which is far from straightforward.

Another problem is that even when specific genetic variants are judged to be harmful, the benefits of knowing this information are not always as clear cut as in the case of bowel cancer. It is an unfortunate reality that most disorders detectable by genomic testing have no proven treatment or means of prevention.

For instance, particular gene variants may put you at risk of developing dementia in your 60s. But if there was nothing you could do to prevent it, would you want to know?

Even when treatments are available, the benefits of knowing you have a certain may not outweigh the disadvantages.

Consider that genomic testing finds you carry a predisposition to sudden heart death, such as Long QT syndrome. This is an outcome you would certainly wish to avoid. But what if knowing this information caused you to worry more, and the treatment required you to give up sport and take a medication that caused you to feel lethargic every day?

And what if, in the absence of symptoms, your risk of actually dying was only slightly increased compared to the general population? Would you still want to know this information, or perhaps prefer to remain ignorant?

Should we get the test?

The Genome.One clinic at the Garvan Institute in Sydney has addressed some of these concerns by taking a cautious approach.

Genetic counselling is provided before and after testing, and although the whole genome is sequenced, analysis and reporting is limited to just 1% of all genes. Most of these selected genes are associated with heart conditions and cancers, and have been chosen because these diseases are well understood, with treatment strategies available.

Genes that cause untreatable diseases, such as dementia, have deliberately been excluded from analysis. This strategy minimises the risk of harm that may come from the test, but the trade-off is that the likelihood of actually finding something useful is greatly diminished. In fact, Genome.One reportedly estimates only 5-10% of people tested will receive an abnormal result; that is, one that will show them to be at risk of .

While it is hard to argue against a test that just might save your life, currently there is insufficient evidence that the benefits of genomic testing outweigh the risks. Even for those who can afford the price tag of A$6,400, there are probably more effective targets for our health-related spending. Like many years of gym membership, for example.

Explore further: Routine genomic testing is feasible, but only a subset of patients benefit

Related Stories

Routine genomic testing is feasible, but only a subset of patients benefit

June 5, 2017
Genomic testing of tumor samples can enable personalized treatment selection, where targeted treatments are matched to genetic changes in the tumor. Although a growing number of patients with advanced cancers receive some ...

Genomic data sharing is critical to improving genetic health care

January 5, 2017
There are an estimated 5,000 - 7,000 rare genetic diseases, each of which can vary dramatically and be caused by a multitude of different genetic changes. Even common diseases with genetic influences may also have rare variants ...

Canadians' preferences for receiving incidental findings from genetic testing

March 9, 2015
Although many people value receiving information about incidental findings identified from genomic sequencing, not everyone wants to know about genetic conditions regardless of potential health implications, found a study ...

New study validates usefulness of genomic medicine in children with neurologic disorders

December 3, 2014
Results from more than 100 families with children affected by a broad range of neurologic and developmental disorders who underwent genomic testing to end their quest for a diagnosis, were published today in Science Translational ...

Cheap genome tests to predict future illness? Don't hold your breath

January 20, 2014
Sydney's Garvan Institute is this week promoting its acquisition of an Illumina machine which it says can sequence the whole human genome for $1,000. The institute hopes genomic sequencing will become widely available in ...

Genetic counseling helps determine risk for hereditary cancers

November 15, 2016
Knowing your family history is a key part in understanding your risk factors for certain diseases. While you're gathering with family this Thanksgiving, get to know more about your family's health history and how it could ...

Recommended for you

Forgotten strands of DNA initiate the development of immune cells

September 21, 2017
Intricate human physiological features such as the immune system require exquisite formation and timing to develop properly. Genetic elements must be activated at just the right moment, across vast distances of genomic space.

Genome editing reveals role of gene important for human embryo development

September 20, 2017
Researchers have used genome editing technology to reveal the role of a key gene in human embryos in the first few days of development. This is the first time that genome editing has been used to study gene function in human ...

A piece of the puzzle: Eight autism-related mutations in one gene

September 19, 2017
Scientists have identified a hotspot for autism-related mutations in a single gene.

Scientists identify key regulator of male fertility

September 19, 2017
When it comes to male reproductive fertility, timing is everything. Now scientists are finding new details on how disruption of this timing may contribute to male infertility or congenital illness.

New assay leads to step toward gene therapy for deaf patients

September 18, 2017
Scientists at Oregon State University have taken an important step toward gene therapy for deaf patients by developing a way to better study a large protein essential for hearing and finding a truncated version of it.

Genomic recycling: Ancestral genes take on new roles

September 18, 2017
One often hears about the multitude of genes we have in common with chimps, birds or other living creatures, but such comparisons are sometimes misleading. The shared percentage usually refers only to genes that encode instructions ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.