NEW YORK — The American College of Medical Genetics and Genomics has updated its practice guideline for evaluating hearing loss to better reflect the state of genetic testing for causes of the condition.
An earlier guideline, issued in 2014, still broadly represents current clinical practice, the developers noted. That guideline was developed by an ACMG working group and incorporated the views of not only medical geneticists but also experts in otolaryngology, audiology, genetic counseling, and genetic testing. It also represented hearing loss researchers and incorporated findings from the published scientific literature. As part of a periodic review, a new working group recently evaluated the existing recommendation.
The updated guideline, which aims to better reflect recent advances in next-generation sequencing-based tests for genetic causes of hearing loss, were presented on Tuesday in the journal Genetics in Medicine.
"Thanks to the emergence of [next-generation sequencing] technologies and associated bioinformatics tools, the knowledge regarding [hearing loss (HL)] has expanded in the last few years especially in the areas of genetic testing, gene-disease relationship, and variant curation," first author Marilyn Li from Children's Hospital of Philadelphia and the University of Pennsylvania Perelman School of Medicine said in an email. "These advances in knowledge and technology also mandated the revision of the algorithm for the clinical and diagnostic evaluation of HL."
Between two and three infants per 1,000 children born in the US have hearing loss, and about 60 percent of that hearing loss is genetic. The working group noted that early detection of hearing loss in newborns is critical to being able to intervene to promote language development.
According to the new guidelines, newborns and infants with hearing loss should undergo a comprehensive evaluation that encompasses patient and family medical histories, a three-generation pedigree, and a physical examination. Depending on whether those assessments indicate a syndromic or nonsyndromic etiology for the hearing loss, the recommendations suggest different genetic testing strategies. About 30 percent of genetic hearing loss is syndromic, with the rest nonsyndromic, and more than 400 genetic syndromes include hearing loss as a feature.
If a syndromic genetic etiology is suspected, genetic testing should be pursued to confirm the diagnosis, either through single-gene testing, panel testing, or other approaches, depending on the clinical findings. However, if a nonsyndromic etiology is suspected, then a tiered diagnostic approach should be pursued, starting with a hearing loss gene panel and followed by genome-wide testing if the panel test is negative.
Genetic counseling, the recommendations added, should accompany testing and be conducted in a linguistically and culturally sensitive manner. Additionally, non-genetic testing, such as testing for cytomegalovirus, CT scans, and MRIs, could also complement genetic testing.
The recommendations further noted that people for whom no underlying cause is found should undergo follow-up testing or examination every three years.
Meanwhile, the recommendations for adults with hearing loss — between 40 percent and 50 percent of the population experiences some hearing loss by the age of 75 — suggest that the evaluation should be guided by the age of onset and other characteristics of their hearing loss.
Going forward, the working group said that genetic testing is likely to become even more of a critical component of newborn screening for a range of conditions, including hearing loss, as sequencing costs decline and as knowledge of the effects of various genetic variants on those conditions increases.
"The new clinical practice resource document has gone through the member review process and revisions," Li added. "After one to two years, the practice resource should be reevaluated for its implementation/adoption via member survey and/or other measures, including but not limited to literature search, and for new developments in the field."