Enhancing diagnosis of hereditary hearing loss
Eye on Innovation
Hearing loss impacts thousands of people in the United States every year. Among children and young adults who are deaf or hard of hearing, 50% have an underlying genetic cause of their condition. Identifying hereditary hearing loss and pinpointing the genes responsible for it are crucial to crafting an effective long-term treatment plan for those patients.
Mayo Clinic Laboratories' new AudioloGene Hereditary Hearing Loss Panel represents a significant step forward in the diagnosis of this condition. Developed by Mayo Clinic's Genetics and Genomics Laboratory in conjunction with Lisa Schimmenti, M.D., a Mayo physician who specializes in genetic conditions associated with hearing loss, this testing panel offers the most comprehensive genetic assessment for hearing loss available today.
The test analyzes 160 genes, assessing for both nonsyndromic and syndromic hearing loss. "There are a lot of individuals for whom hearing loss is only a small part of their genetic picture, and they fall into the syndromic hearing loss category," says Nicole Boczek, Ph.D., co-director of the Genetics and Genomics Laboratory. "These conditions can be very difficult to assess clinically, especially if they present at the newborn stage. So we decided to add more of those genes to our panel to help the ordering provider identify the syndromic conditions early."
"KNOWING IF A CHILD OR YOUNG ADULT HAS A SYNDROMIC FORM OF HEARING LOSS HELPS WITH MANAGEMENT AND PREVENTS CLINICAL SURPRISES WHEN ANOTHER HEALTH ISSUE ASSOCIATED WITH HEARING LOSS ARISES," DR. SCHIMMENTI ADDS.
Diagnosing syndromic conditions promptly can play a central role in the proper management of hearing loss. For example, Usher syndrome — a rare genetic disorder — often causes hearing loss in infants. As it progresses, the condition frequently leads to loss of sight, as well. It's important to arrive at a diagnosis of Usher syndrome quickly because it informs which therapies are most appropriate.
"You might consider oral language in addition to sign language because the patients will likely have vision impairment eventually," Dr. Boczek says. "Establishing that early on allows clinicians to pursue the best management for those individuals."
The technology that undergirds this new hearing loss panel includes a custom capture next-generation sequencing reagent that identifies single nucleotide variants, and small insertions and deletions, as well as copy number variants. The panel also uses ddPCR technology to ensure a more accurate test for the detection of mitochondrial DNA variants — a feature that is uncommon in other hearing loss tests. This has the benefit of significantly reducing false negative results, and it's one of the few methods that can achieve absolute, rather than relative or indirect, quantification of hetroplasmy.
Finally, because it was developed with input from clinical specialists, and it covers such a wide range of genes, Mayo's hearing loss testing panel reduces the need for supplemental testing, providing clear, clinically meaningful results faster. "Under the advice of Dr. Schimmenti, we added many syndromic conditions to the panel. Some of the other labs test for some of them, but not all," Dr. Boczek says. "The result is a test that is more all-encompassing than many other tests out there."
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