HGTD This week, 19 June 2020: NEW Orange Breed Relevance Rating (BRR)

The continued review of breed-specific tests for assigning relevance ratings, and ongoing discussions with genetic experts has led to a refinement of the breed relevance ratings (please see: BRR) . To better accommodate the spectrum of genetic test validation, we’ve added a new orange BRR. 

The orange BRR indicates where all current available evidence has been reviewed, but the relevance is inconclusive. It could be that a mutation is detectable in a specific breed, but that there is no evidence that this correlates with clinical development of the disease/phene. It could also be that there is evidence that testing for the mutation does not correlate with the clinical development of the disease. One example is the wire-fox terrier and degenerative myelopathy. Despite research indicating a 94% mutation frequency (Zeng et. al, 2014) - meaning that practically every dog the researchers tested for SOD 1 mutation for degenerative myelopathy had 2 copies of the mutation - the development of the clinical signs of DM for the breed hasn't yet been reported. 

In practical terms, this means that while you may still wish to test for the mutation in your breed, or it may be included on any testing panels, there isn’t currently a good reason to prioritize test results in any breeding or other health decisions. Unnecessarily excluding a dog from breeding based on irrelevant or inconclusive test results can be, on balance, very damaging to the genetic diversity of the breed. Thinking back to DM and the wire-fox terrier, this would mean that if breeding decisions were made on DM test results alone, you'd be excluding the vast majority of the dog population where the test does not for this breed seem to predict clinical disease. 

For any orange BRR, it would be worth looking at the test’s breed-specific information in more detail (search for test information HERE) to help put any potential test results into perspective. Wherever possible, the phenes database includes comments directly from the researchers and original test developers. As always, talk to your genetic test provider and/or veterinary scientist if you are concerned about genetic test results.  

And, if you missed it the first time around, you may want to check out the previous blog including updated breed relevance ratings, and breed-specific publications, HERE. 

References:

Zeng R., Coates J.R., Johnson G.C., Hansen L., Awano T., Kolicheski A., Ivansson E., Perloski M., Lindblad-Toh K., O'Brien D.P., Guo J., Katz M.L., Johnson G.S. (2014) Breed Distribution of SOD1 Alleles Previously Associated with Canine Degenerative Myelopathy. J Vet Intern Med 28: 515-521

Photo thanks to: Engin Akyurt, via Pexels