Читать книгу Pet-Specific Care for the Veterinary Team - Группа авторов - Страница 278

Several commercial genetic testing laboratories offer breed‐specific “panels” of DNA tests versus running individual tests. However, in many instances, tests may be offered that have no relevance to causing clinical disease in a specific breed. A test may be offered based on a single published report, from a research colony, or from a related breed. Test results are of no consequence if a disease is not clinically documented in the specific breed population. Sources should be consulted to identify valid genetic tests in each breed.

Some commercial laboratories have developed gene chips that test for hundreds of SNPs from a single DNA sample (usually a cheek swab). This is far more cost and time efficient than sending out DNA samples to multiple laboratories for individual gene tests. If a SNP is the sole cause of the disease, then these are direct genetic tests. However, many of these SNPs are associated with a larger mutation and so are actually linked marker tests. These are susceptible to false‐positive and ‐negative results. If decisions of treatment or breeding are being made, they should be based on direct mutation tests.

While multiplex (panel) testing provides a more cost‐efficient way to do genetic testing, the majority of individual SNP results are of no consequence except to single breeds or subsets of breeds. There are many mutations that cause disease in one or a few breeds, however the mutation is present in many other breeds and does not cause clinical disease. This is because in the other breeds, additional mutations are not present that make the testable mutation a disease‐causing gene. The sod1 mutation for degenerative myelopathy and the cord1 PRA mutations are examples of liability genes that contribute to disease in only a handful of breeds but may be detectable in almost all breeds. A carrier or even “affected” test result for these mutations must be ignored in breeds not prone to the specific disorder.