Ok, as per a request, this is being started as a new discussion. :-) The question, of course, is if this relatively new test should be part of the screening tests we expect (or at least expect to see) when we are choosing a puppy.
First, my initial post, then I'll put in a new response:
I have been puzzling over the DM test, and it makes me uncomfortable. Apparently there is a fair amount of controversy over it. So far all dogs with DM have a certain genetic marker, but it is not clear what percent of dogs with this marker develop the disease. Nor is it clear that there are not other genetic markers involved.
This is something I know a fair amount about. I have an autoimmune condition called ankylosing spondylitis, which is an inflammatory and progressive arthritis of the spine. There is a genetic marker for the disease which is present in roughly 92% of people with AS. I lack this marker. However, over 90% of people who have this genetic marker will NEVER, I repeat NEVER get AS.
Moreover, more recent long-term studies have uncovered at least 2 other genes implicated in the disease, or expression of it.
I would have zero confidence that a test for DM, which is an auto-immune disease, would at this early stage of research give any real indication of how likely an "affected" dog is of coming down with the disease. I would also have virtually no confidence that a dog that that tested clear would not come down with a disease that is symptomatically so similar to DM as to be indistinguishable in its end result. Why is that? Because I highly doubt that research in the field of autoimmune disease in dogs is so far ahead of that in humans that they can say definitively what genes cause this very sad condition.
It leaves more questions than answers. If indeed a relatively large portion of the population tests positive, but it turns out that as in humans the huge majority of "positive" animals will never, ever develop the disease, what would we do by screening them out of the gene pool?
I think the testing should be done for research, but to offer it as a breeder screening as a means of somehow insuring that a pup won't be affected is perhaps getting a little ahead of the current status of the research.
These auto-immune conditions are very complicated, are likely caused by several sets of genes causing expression or suppression of symptoms, and moreover more than likely have an environmental component that "triggers" the onset of disease activity.
Edit: This is from the very website that is conducting the research and testing for DM:
http://www.caninegeneticdiseases.net/DM/testDM.htm
"The “A” allele is very common in some breeds. In these breeds, an overly aggressive breeding program to eliminate the dogs testing A/A or A/G might be devastating to the breed as a whole because it would eliminate a large fraction of the high quality dogs that would otherwise contribute desirable qualities to the breed."
The Pembroke Welsh Corgi is one of the breeds with a very high incidence of Positive or Carrier dogs. Don't count on a flood of breeders offering up the results of their dogs tests any time soon.
Indeed, from the same site:
"Summary: We recommend that dog breeders take into consideration the DM test results as they plan their breeding programs; however, they should not over-emphasize this test result. Instead, the test result is one factor among many in a balanced breeding program. "