Genetic testing
Genetic testing has been a boon to medicine by enabling us to predict disease risk and by providing insight to help guide treatment decisions. However, many associations between genes and diseases may be lacking, so the selection and interpretation of genetic tests requires rigorous evidence. (Photo: UHN Research)

Genetic discoveries have made huge strides in recent decades. These advances and new technologies are revolutionizing our access to genetic testing. Some companies offer "at-home" genetic tests that make it as simple as sending in a mouth swab to the company. Accredited labs also offer tests for specific genes believed to be linked to various diseases.

These tests can provide insight into your risk for certain diseases. However, not all genes cause disease, and care must be taken when creating a screening test for a given gene. Clinicians who are not experts in genetics or a particular disease may also place undue faith in lab tests: they may assume that because a lab is offering testing for a specific gene, it must be linked to a disease.

An international team led by Dr. Michael Gollob, Toronto General Research Institute Scientist and Peter Munk Research Chair in Cardiovascular Molecular Medicine, recently used an evidence-based framework to investigate the appropriateness of genetic tests.

The team focused on genetic tests used for Brugada syndrome - a rare heart rhythm disease that puts around one in 2000 people at risk for sudden cardiac death.

For the study, the researchers included a group of 21 genes for Brugada Syndrome that are currently tested by labs in the United States and internationally. Three teams independently reviewed each gene to determine whether sufficient evidence exists to link them with Brugada syndrome.

Only one gene, known as SCN5A, was definitively linked to Brugada syndrome - while evidence was lacking for the other 20 genes. All three teams independently agreed on these results.

These results are troubling because they reveal that many genetic tests may fail to provide real insights. Use of these dubious tests could lead to incorrect diagnostic conclusions, unnecessary testing, treatments and anxiety and stress for patients and families.

As to why the laboratories offer so many unproven tests, Dr. Gollob says laboratories do not have to justify the inclusion of genes for clinical testing.

"It's possible that the increasingly competitive marketplace and a 'more is better' mentality has led to rapidly expanding gene panels," he says. "Our findings indicate that more rigorous standards are required to ensure that genetic tests are meaningful."

This work was supported by the US National Human Genome Research Institute. Dr. Gollob is supported by a Peter Munk Research Chair in Cardiovascular Medicine from the Toronto General & Western Hospital Foundation.

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