The application of genetic testing for the diagnosis of diseases.

Despite a widespread belief that genetic testing is used for diagnosis, this technology can almost never be applied for this purpose when used in isolation. In fact, this is why a genetic test does not need to be requested by a veterinarian.

When the results of a gene test related to a specific disease show that a dog carries two copies of the variant, the animal's entire context must be taken into account. This result in asymptomatic dogs, and especially in young dogs, demonstrates the future risk of developing the disease. After all, the vast majority of testable genetic diseases are not congenital, meaning they are not present in newborns. This information can (and should) be used in preventive medicine through nutritional, behavioral, and even pharmacological management in some cases, which may delay the onset of clinical signs in dogs at increased risk. In other words, genetic information is useful for personalized preventive medicine.

On the other hand, when the same result is seen in a dog with clinical signs compatible with the disease, and other causes for these signs have already been ruled out, this is the situation where genetic testing contributes significantly to the diagnosis. There are several examples of this type of application, but perhaps the best known is a neurological disease called "degenerative myelopathy," which is very common in German Shepherds and Corgis, and also present in many other breeds such as Bernese Mountain Dogs and Boxers.

Degenerative myelopathy is a neurological disease of the elderly, caused by the death of neurons that innervate the hind legs, initially. This dog begins to have difficulty walking, presenting progressive lameness. These signs can be confused with many other diseases, especially some orthopedic diseases. If, at the onset of clinical signs, this dog undergoes genetic testing for this disease, and the test shows that it has two copies of the SOD1 gene variant, this data, together with the clinical signs, will be useful for reaching a diagnosis.

In any area of ​​human or veterinary medicine, the final diagnosis of a disease is a crucial step: it enables targeted and effective treatment for treatable diseases, prevents unnecessary interventions on the animal, and saves the entire family emotional and economic stress.