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Breaking News: Genetic Testing Can Explain Hearing Loss and Guide Therapy

Scheck, Anne

doi: 10.1097/01.HJ.0000416273.98729.a8
Figure. i

Figure. i

Audiologists have been predicting for years that a single blood sample would be used to quickly detect a multitude of underlying genetic causes for hearing loss. A test at the University of Iowa in Iowa City does just that, screening genome sequences associated with syndromes ranging from Pendred to Usher and for genes linked to hearing deficits. What does this advance mean to those who treat the hearing impaired?

A lot, said Jeff Simmons, who coordinates the Cochlear Implant Center at Boys Town National Research Hospital in Omaha, NE. “I think it has multiple uses,” he said, aside from being able to pinpoint a cause. “From a clinician's point of view, [genetic testing] can help tell us where we want to go in terms of remediation.”



Such testing also may expose evidence of a condition with a cluster of other complications, indicating involvement of other organs. Treatment decisions can often be difficult in audiology, especially with the progression or stabilization of early hearing loss and whether it is permanent or temporary. Genetic studies can provide information to help guide therapy, added Mr. Simmons, who has chronicled his experience with genetics in pediatric audiology. (See FastLinks.)

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Cost and Turnaround Time

Investigations during the past decade have isolated X-linked genes as well as autosomal dominant, autosomal recessive, and mitochondrial genes related to hearing loss. It was not until genome-sequencing technology, a fairly recent advance that avoids traditional gene mapping, that precise mutations in DNA could be identified without a laborious process of multiple procedures, reported genetics investigators for the National Institutes of Health. (Hum Mutat 2012;33[4]:5.) Individuals were screened for hearing loss using these targeted techniques, showing similar mutations but with specific variations, according to a statement from BioMed Central, an open access publisher. (See FastLinks.)

Uncovering this only a few years ago would have taken months or even years in an often tedious process of elimination. OtoSCOPE genetic testing, as the University of Iowa calls it, is billed as “the first truly comprehensive genetic test” for hearing loss. It was developed in part with a grant from the NIH and in conjunction with the Human Genome Sequencing Center at Baylor College of Medicine in Houston. (See FastLinks.)

No patent exists for OtoSCOPE, and no formal advertising campaign or national launch is planned to promote it. But the cost savings is enormous at $2,000 per test; previous gene-by-gene testing could rack up a bill of $75,000, according to a statement from the University of Iowa. (See FastLinks.)

When the test was finally put into large-scale use this past January, it was at Iowa's Molecular Otolaryngology and Renal Research Laboratory where studies continue processing samples from across the country, according to one of the test's developers, Eliot Shearer, MD. “We are a nonprofit lab trying to do good work,” he explained. “Obtaining results from UI's lab generally has taken about three months, but technology will be added [through] an in-house DNA sequencer, which will mean substantial reductions in that turnaround time, depending on volume.”

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Figure. E

Dr. Shearer credited groups at Harvard and in Israel with investigations that assisted in refining the technology, and noted that studies at Emory University in Atlanta also provided helpful research.

OtoSCOPE follows widespread predictions that new genome-sequencing techniques would “tackle the unsolved challenges unconquered by previous genomic technologies,” and that the effect “will be far reaching and likely change the field for years to come.” (J Genet Genomics 2011;38[3]:95.)

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To Know or Not to Know

Genetic testing, however, can be confusing for parents of children with unexplained deafness. It can be a relief to know that there is an underlying cause, but it can also be stressful, according to past studies. Some parents blame themselves for defective genes; others do not appreciate how the information can influence treatment decisions, and misconceptions are common. (Am J Audiol 2007;16[1]:57.)

The procedure can elicit concern and support, according to a focus group study of consumer attitudes toward genetic testing in heritable deafness. Advocates among study participants considered the underlying reason for hearing problems to be important information. But others in the study worried that test results could influence their future reproductive decisions. (Genet Med 2006;8[12]:779.) That may be true, said Jerry Olmstead, who has been hearing impaired since having the mumps as a boy.

As a chapter leader for the Hearing Loss Association in Washington State, Mr. Olmstead has often wondered if his childhood illness is the sole explanation for his early hearing impairment, but he had no way of knowing. “I had concerns about it when I started a family,” he said, adding that his children have normal hearing. “I used to think, though, that if there were a way of knowing, I might want to know.”

Mr. Olmstead said he was not sure if he could take the test if he were in the same situation today. “But it is a distinct possibility.”

The American Academy of Audiology has periodically published advice on audiologists’ roles in genetic screening, which boils down to referrals for genetic counseling and then supportive follow-up for those who are tested. (See FastLinks.)

Brushing up on genetics may now be needed, however. An enterprising audiology doctoral student at Gallaudet University decided to find out how familiar audiologists are with current genetic testing information. Many of the study participants were confident they had a good grasp on the information, but more than half could provide the correct answer for only one of six basic questions. A majority, however, expressed interest in participating in continuing medical education on genetics, reflecting a desire to stay up-to-date on developments in the field. (See FastLinks.)

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