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The 'Fantasy World' of Incidental Findings

As the American College of Medical Genetics and Genomics this week issued recommendations regarding the release to doctors and patients of incidental genetic findings from clinical sequencing studies, Caroline Wright at Genomes Unzipped questions whether the term "incidental" is appropriate for describing such findings in the first place.

"One of the things that has always bothered me about the [incidental findings] debate in genomics is the idea that these findings are ‘incidental’ at all – that we just can’t help but stumble upon significant variants while reading peoples’ genomes," Wright says. "In this fantasy world, researchers and clinicians who don’t share [incidental findings] with people must be hiding them somewhere, stowed away in a drawer marked ‘Confidential’."

Wright speculates that this perception is "partly a result of the frequent comparison with medical imaging, where radiologists really can’t help but see [incidental findings]. However, the situation in genomics is less like a spot-the-different picture and more like a well-worded Google search."

As an example, she notes that analyzing someone’s genome for a genetic predisposition to breast cancer "is unlikely to incidentally throw up the fact that they also have a dominant neurodegenerative disease – the mutations are in different locations and will not both be extracted by a computational search for either one of them."

Wright argues that "simply stumbling upon" clinically actionable incidental findings in a whole genome sequence is "highly unlikely" and notes that the real question should be whether researchers have an obligation to actively look for certain types of variants when conducting whole-exome or whole-genome sequencing.

She says that throwing away the “stumble strategy” would "allow disclosure of specific classes of variants to become an evidence-based decision rather than a process of random luck."

Meanwhile, the Nature News Blog reports that there has been some criticism about the ACMG's recommendations on incidental genetic findings being "too conservative."

ACMG acknowledges in a document outlining its recommendations that it sought to reach a compromise between "genetic libertarians who feel that patients have the right to full and complete accounting of all possible risks,” and "genetic empiricists who believe that there is insufficient evidence about the penetrance of most pathogenic variants in the general population to warrant the sharing of any incidental findings."

Gholson Lyon of Cold Spring Harbor Laboratory tells the Nature News Blog that the recommendations are “biased heavily” in favor of the empiricists and could limit the ability of researchers to analyze clinical genomes for research.

On the other end of the spectrum, Nancy Spinner, chief of the division of genomic diagnostics at the Children’s Hospital of Philadelphia, tells the blog that her team actually takes "a little more of a conservative approach” than the ACMG recommends.

ACMG says that its recommendations "should, and will, evolve, as further empirical data are collected on the actual penetrance of these variants, and on the health benefits and costs that might follow from their disclosure as incidental findings."