Dr Carissa Bonner

Is it helpful to know you are at risk of sudden cardiac death if no-one can tell you how great the risk is?

This is the question being posed by researchers from the University of Sydney who have found high levels of anxiety and misunderstanding among people who have had a positive genetic test results for hypertrophic cardiomyopathy (HCM).

As genetic testing  goes mainstream, the number of ‘silent carriers’ being identified is growing, but little is known about the degree of risk this group faces in developing serious outcomes such as sudden cardiac death, according to Dr Carissa Bonner and researchers from the University of Sydney’s School of Public Health.

Writing in the Journal of Genetic Counselling, they note that with an estimated prevalence of 1 in 200, HCM follows an autosomal dominant pattern, with first degree relatives having a 50% chance of inheriting it. Those with a family history may be offered the test in addition to clinical surveillance.

But the researchers, who interviewed 32 people most of whom were ‘silent carriers’, found that testing positive could have big psychological impacts on carriers, such as initial shock, worry about their children and sudden death, an increased awareness of heart sensations and uncertainty about their disease status and future risk.

This then drove some people to restrict careers and physical activity, carry out investigations to seek assurance.

Some had expensive life insurance denied.

To date, there is data suggesting silent gene carriers who remain clinically unaffected in adulthood have a very low risk of converting to the HCM phenotype and very low risk of adverse outcomes, they write.

“The issue facing patients is that genetic test results only indicate that they may be at risk of developing hypertrophic cardiomyopathy, not that they already had the disease,” Dr Bonner said.

“The question we’re asking is: Would they be better off not knowing?”

However, the study authors identified that negative impacts were more common in those who had misunderstood the implications of their carrier status.

“The findings illustrate the importance of cardiac genetic counselling prior to the test, and the need for more comprehensive communication around the meaning and implications of the test result so patients can be better informed to make life decisions,” the study concluded.