Study Of Sudden Cardiac Death Exposes Limits Of Genetic Testing : Shots - Health News Some genetic tests for a common cause of sudden heart failure can be wrong, researchers say, because the underlying science didn't take into account racial diversity.

Study Of Sudden Cardiac Death Exposes Limits Of Genetic Testing

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We're going to hear about genetic testing. It is done at medical labs to help people identify risks to their health. But genetic tests are not always as reliable as you would hope. Just take heart disease genes. Some of these genes have been misidentified because researchers did not get the right racial balance in their testing. Here's NPR's Richard Harris.

RICHARD HARRIS, BYLINE: A heart condition called hypertrophic cardiomyopathy is a leading cause of sudden heart death. Dr. Isaac Kohane at the Harvard Medical School says it follows a classic genetic pattern, which should make it easy to track through gene testing.

ISAAC KOHANE: You don't need two copies of the mutated gene. Just one copy, and you have the disease, so it's a textbook case.

HARRIS: In New York City, Tarika Mingo knows all too well the consequences of inheriting this trait. Shortness of breath and other worsening symptoms sent her to the doctors two years ago, and they diagnosed the disease in her.

TARIKA MINGO: So ten months ago, I had open-heart surgery. I had what's called a septal myectomy and a mitral valve repair.

HARRIS: Still, she lives with the ongoing consequences of this disease, including frequent doctor trips and daily medications.

MINGO: The heat is not my best friend, so it limits my social activities. We just had a heat wave, and I was stuck in the house.

HARRIS: Testing revealed a genetic variant in her, which is apparently the risk factor that runs through her family. Each member of her immediate family has a 50/50 chance of carrying the variant. Her 29-year-old sister has been having heart problems.

MINGO: And I've encouraged my siblings to get tested genetically.

HARRIS: But the genetic testing for this disease isn't as reliable as you would expect any. One of about a dozen genes can be involved in the disease, and each has many different variants. Dr. Kohane's lab at Harvard was cataloguing those. They expected to find the dangerous trait in 1 in 500 people, since that's how often the disease appears.

KOHANE: We saw that the variants that were ostensibly causing the disease seemed to add up to much more than 1 in 500.

HARRIS: This was specifically the case in people with African ancestry.

KOHANE: Something must be wrong.

HARRIS: Kohane and his colleagues have now explained that problem in the New England Journal of Medicine. It seems that researchers who originally identified some of those variants didn't take enough care to include healthy people of African descent in their studies. As a result, some of the gene variants in African-Americans are, in fact, false alarms and not linked to the disease. One consequence could well affect college athletes. Dr. Barry Maron at the Tufts Medical Center consults for many schools who come to him when they have uncertain results from physical cardiac tests. They may then run genetic tests.

BARRY MARON: In that situation, a false-positive test could give a false diagnosis to an athlete who doesn't have hypertrophic cardiomyopathy. And this could lead to disqualification from competitive, intense sports.

HARRIS: And the results extend far beyond athletes, to families like Tarika Mingo's.

MARON: False positives are difficult because they're indelible.

HARRIS: The fear can never be erased. And Tarika Mingo says if doctors told her the trait identified in her family was actually benign, she wouldn't put much trust in that. Doctors Maron and Kohane draw a larger lesson from all this. Even a disease like this with seemingly simple genetics turns out to be pretty complicated.

KOHANE: It just turns out that the genome is as complicated and unique as each one of us.

HARRIS: So people who are expecting tidy yes-or-no answers from any genetic test need to dial back their expectations. Richard Harris, NPR News.

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