Re: Absence of “High Penetrance” in SNP Genomic Services

Michael Nierenberg — Wed, 22 Oct 2008 13:43:48 -0000

Mr. Andrew Yates offers the following comment in Absence of “High Penetrance” in SNP Genomic Services about espousing the uselessness of genetic testing by companies such as Navigenics:
“The reality is that except for a few enthusiasts (like anyone in the DNA Network, including myself), existing SNP genomic services just aren’t that useful. It’s not useful to know that one has a 7% lifetime risk rather than a 5%. I need to know risks of about 40% and higher.”
In response to Mr. Andrew Yates I offer the following information about lifetime risk assessments offered by Navigenics (www.navigenics.com).
On the Navigenics HealthCompass six conditions have a lifetime risk potential that exceeds 35% (Five conditions exceed 40%). Since some conditions are less common in the population, it is useful to also consider relative risk, as opposed to absolute risk.
Half of all 23 conditions reported have a relative risk (compared to the average genetic risk in the general population) greater than 2; seven conditions, greater than 3; and three conditions greater than 4. For comparison, this level of relative risk is in line with other well-accepted, commonly used risk factors such as positive family history and environmental risk factors (high lipids, age at menopause etc.)

I hope this clarifies things for Mr. Yates who can now feel better about being an enthusiast.
I would also ask Mr. Yates to reconsider his statement about why Navigenics is not doing BRCA testing. Patent considerations aside, it is of import only in about 5% of breast cancer cases (those with “extreme” positive family histories and early age of onset). The contribution of BRCA1/2 mutations in sporadic breast cancers has not been determined conclusively. Our preference is truly to offer a test that is applicable to the majority of individuals. We are cognizant that in a minority of people BRCA testing is important and have addressed this issue on our web site in several places. We realize that no test is complete in and of itself; otherwise people would have heart surgery based only on a treadmill. So, I would ask Mr. Yates to please give us credit for more than trying to get around patent considerations. We are enthusiasts as well.

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Re: Absence of “High Penetrance” in SNP Genomic Services