Genetic tests for an inherited heart disorder are more likely to have incorrect results in black Americans than in whites, according to a new study that is likely to have implications for other minorities and other diseases, including cancer.
Mistakes have been made because earlier research linking genetic traits to illness did not include enough members of minority groups to identify differences between them and the majority white population or to draw conclusions about their risks of disease.
The new study, published Wednesday in The New England Journal of Medicine, focused on hypertrophic cardiomyopathy — a thickening of the wall of the heart that can cause abnormal rhythms and sudden death. The condition often has no symptoms, but can cause young athletes to pass out or even die during the intense activity of their sport. It can be caused by inherited mutations in one of 10 to 20 genes, and affects one in 500 people in the United States. More than 1,000 mutations have been linked to the condition.
Genetic testing can identify people who have suspect mutations, and is frequently offered to family members of those who have the disease. But now researchers have found that after genetic testing, black people are more likely than whites to be told mistakenly that they are at risk.
The misdiagnosis can have big repercussions. Besides the emotional stress of being told one has a potentially fatal heart condition, there is the time and expense needed for medical follow-up. Active young people may be told to drop out of competitive sports, and in some cases even advised to have devices surgically implanted in their chests to prevent sudden death from abnormal heart rhythms.
Mistakes have been more common in blacks because they are more likely than whites to carry certain mutations that, in earlier studies, were thought to cause the disease, said Arjun K. Manrai, the first author of the study and a researcher in the department of biomedical informatics at Harvard Medical School. Later research has proved those mutations to be harmless.
The conclusions are based in part on analyzing large, relatively new databases that contain information about mutations and their occurrence in various racial and ethnic groups.
Some laboratories that perform the genetic tests have not kept up with the science, and are still mistakenly telling patients that their mutations are dangerous, according to Dr. Isaac S. Kohane, the senior investigator on the study. Even the labs that do keep up may not contact past patients to let them know that their test results are no longer valid, he said. ..