Genetic Testing for Cardiomyopathy Less Useful for Racial Minorities

Minority groups have less access to genetic testing for cardiac disorders and other diseases. And now a new study confirms what geneticists have long suspected: that this disparity in access has a negative impact on the usefulness of such tests in people from these groups, even when they’re able to undergo testing.

Among patients getting genetic testing due to a suspected diagnosis or family history of cardiomyopathy over a 14-year period, a conclusive, positive result was more likely in white individuals (29.0%) than in people from underrepresented minority groups (18.4%; P < 0.001), including black, Hispanic, Native American, Alaskan Native, Hawaiian, and South Pacific Islander individuals. The positive detection rate was nonsignificantly lower in Asian patients (25.0%; P = 0.12).

Moreover, an inconclusive result was more likely to be seen in underrepresented minorities (39.8%) and Asians (39.2%) than in white individuals (24.6%; P < 0.001 for both comparisons), Latrice Landry, PhD, and Heidi Rehm, PhD (Brigham and Women’s Hospital, Boston, MA), report in a study published online February 28, 2018, ahead of print in JAMA Cardiology.

“The reason for that, which we speculated on, was because there is less of an evidence base built up for defining the significance of variants by having observed them in past patients,” Rehm told TCTMD. “Variants tend to be specific to populations, so if you haven't studied the population, you don't have a lot of data on the variants in that population.”

Not Enough ‘Normals’ or ‘Affecteds’

There are two main reasons for the lack of data on genetic variants in minority populations: historically poor recruitment of people from these groups into research studies—which have tended to enroll individuals with European ancestry—and worse access to healthcare, including genetic testing, due to socioeconomic disadvantages. Thus, there is little information from “normal” populations of people from underrepresented minorities or from patient groups with confirmed diagnoses of genetic disorders.

“We don't have enough of the normals and we don't have enough of the affecteds, and you need both to really make good diagnoses,” said Glenn Gerhard, MD (Temple University, Philadelphia, PA), who co-authored a viewpoint in the journal discussing the topic.

The impact of these issues on the usefulness of genetic testing in underrepresented minorities is borne out in the study by Landry and Rehm, which was a cross-sectional analysis of 5,729 people who underwent genetic testing for cardiomyopathy at the Laboratory for Molecular Medicine at Partners Healthcare Personalized Medicine in Cambridge, MA, between October 2003 and December 2017. Most individuals were white (79.2%), 6.1% were Asian, and 14.7% were from an underrepresented minority group.

Moving in the Right Direction

Speaking with TCTMD, Elizabeth McNally, MD, PhD (Northwestern University Feinberg School of Medicine, Chicago, IL), who co-authored an editorial accompanying the study, called the findings “rather striking,” adding that they confirm what had been a concern among geneticists who have been working hard to overcome the problem.

And McNally, Rehm, and Gerhard all agreed that progress is, in fact, being made, at least on the research side.

The National Institutes of Health has begun mandating more diversity in research studies, and public databases of genetic information from US-based populations—with better representation of minority groups—have been expanding. The All of Us research program, for example, has the goal of gathering data, including DNA samples, from at least a million people living in the United States.

However, there’s still room for improvement on the clinical side, Rehm said. “There's no mandate [for better representation] there, and in fact, what largely drives this is insurance coverage and payment for testing and that's not being helped by anyone,” she said. “And so there's still significant disparity on the clinical testing arena, even if the research side is getting better.”

Even so, Gerhard saw some signs to indicate that difficulties in getting people tested are starting to ease. In recent years, he noted, sequencing technology has improved substantially while dropping in cost. The out-of-pocket cost to a patient has fallen from the thousands of dollars to perhaps $150 to $250, he said. In addition, the utility of genetic testing is now supported by guidelines from professional societies.

Gerhard said that even though challenges remain in getting patients tested, he’s hopeful that the combination of efforts on the research and clinical sides will help close the gap in the utility of genetic testing between racial/ethnic groups within 5 to 10 years.

In the accompanying editorial, McNally with co-authors Lisa Dellefave-Castillo, MS, a genetic counselor, and Megan Puckelwartz, PhD (Northwestern University Feinberg School of Medicine), say that incorporating the expertise of genetic professionals into cardiology practices also will help address the observed racial/ethnic disparities.

Genetic testing “is increasingly playing a more important role for cardiovascular medicine, because there’s a lot of our disorders that we deal with that have a high heritable component,” McNally said, noting, however, that most cardiologists do not have the training necessary to correctly interpret the results of genetic tests.

“So working together with professionals like genetic counselors who are well trained in doing this makes a lot of sense, because it brings the best of both the expertise in cardiology and the expertise in genetics,” McNally said.

She acknowledged that there is a shortage in genetic counselors in cardiovascular medicine and other specialties, an issue that the field is working to address.