The test determines whether the mutated copy of SOD1 is present in the DNA sample submitted. It must be interpreted with caution by a veterinary clinician in combination with the animals clinical signs and other lab test results. The results reported are:

Normal / Normal (N/N, or clear): The dog does not have the mutation and is extremely unlikely to develop degenerative myelopathy. There have been cases, however, in which dogs that tested clear were found to have DM upon necropsy. Normal / Abnormal (N/A or carrier): The dog has one mutated copy of the gene (is heterozygous) and is a carrier but will not have degenerative myelopathy though there has now been some cases of heterozygous carriers developing DM. It will be possible for it to pass the mutation to offspring. A thorough examination of the dogs pedigree and DNA testing should be undertaken prior to breeding a dog with this result. Abnormal / Abnormal (A/A or At Risk): The dog has two copies (is homozygous) for the mutation and is at risk for degenerative myelopathy. Genetics
Breeding risks for degenerative myelopathy can be calculated using the Punnett Square:

If both parents are clear (N/N) then all of the puppies will be clear. If one parent is a carrier (N/A) and one is clear (N/N) each puppy has a 50% chance of being clear and a 50% chance of being a carrier.
If both parents are carriers (N/A) each puppy has a 25% chance of being clear (N/N), 50% chance of being a carrier (N/A), and 25% chance of being affected and carrier (A/A)
If one parent is clear (N/N) and one parent is affected (A/A) then all puppies will be carriers (N/A)
If one parent is a carrier (N/A) and one is at risk (A/A) each puppy has a 50% chance of being a carrier(N/A) and 50% chance of being affected and carrier (A/A)
If both parents are at risk (A/A) then all puppies will be affected and carrier (A/A)

Symptoms
Degenerative myelopathy initially affects the back legs and causes muscle weakness and loss, and lack of coordination. These cause a staggering affect that may appear to be arthritis. The dog may drag one or both rear paws when it walks. This dragging can cause the nails of one foot to be worn down. The condition may lead to extensive paralysis of the back legs. As the disease progresses, the animal may display symptoms such as incontinence and has considerable difficulties with both balance and walking. If allowed to progress, the animal will show front limb involvement and extensive muscle atrophy and paralysis. Eventually cranial nerve or respiratory muscle involvement necessitates euthanasia or long term palliative care.Progression of the disease is generally slow but highly variable. The animal could be crippled within a few months, or may survive as long as three years or more. Causes
The etiology of this disease is unknown.