IPFD friend and collaborator Dr. Jerold Bell, Adjunct Professor Tufts University, and Chair of the Hereditary Disease Committee of the World Small Animal Veterinary Association, has recently circulated a letter about DM testing in French Bulldogs (attached below). According to his research and communication with international neurologists there has never been a confirmed case of DM in this breed, and yet the test is recommended in several countries.
French Bulldogs do have spinal problems, but these are generally due to widespread prevalence of vetebral abnormalities and not DM. Testing - and then perhaps eliminating dogs from the breeding stock based on test results - is not a beneficial strategy for the population.
Part of the problem of wrongly recommended tests may related to the unfortunate use of language for some genetic tests. Results of allele frequencies may be reported as 'clear', 'carrier', or 'affected'. In fact, 'affected' in this case means 'genetically affected' and may or may not relate to clinical disease, as in the case of DM in French Bulldogs, at least as far as we know.
Discussions like these are crucially needed as part of better genetic counselling.
See further discussion on this issue in my talk to the American Veterinary Medical Association.
Here is the letter from Dr. Bell: