When the Test Results are Negative but the Symptoms are Present

It may have happened to you, your friend, a family member, your dog or your horse. A genetic test was run in the hope of finding a reason behind your or their health problems, but the test results were negative. No questions were answered, and the patient was left undiagnosed. For now.

The thing with genetic testing is that it’s still rapidly developing. What we know and understand so far is only a fraction of the information available, and science continues to make new discoveries. Just because we don’t know the answers now doesn’t mean we won’t know them in a few years, as progress is made in this field every year. 

As an example, we can name Equine Juvenile Spinocerebellar Ataxia (EJSCA). It’s a neurological genetic disease affecting American Quarter Horse foals that was identified just this year. However, the case that sparked the attention actually happened five years earlier. In the spring of 2020, in Oregon, an American Quarter Horse foal that appeared healthy and bright at birth developed severe neurological symptoms (ataxia, inability to stand) in its first month of life, and all known tests for neurologic diseases came back negative. At the end, a total of 12 cases of foals with similar symptoms were described, and moreover, the foals were found to be related. Five years forward, the mutation responsible for the disease is known, although yet to be published. This potentially allows us to select parental pairs in such way as to prevent the onset of disease.

A new discovery of a causal gene may not be necessary for a correct diagnosis of a health problem which was left undiagnosed before. It can also be the emergence of new symptoms, which can provide important clues for the overall picture and diagnosis. Another important factor may be technological development, such as hardware upgrades, new algorithms, the advancement of AI technology and updates of information databases. There are many factors, and each of them can be key to a successful diagnosis.

If the disease is genetic, it’s hidden somewhere in the genome. We just may not be able to decode it yet. However, reanalysing genetic data increases the chances of successful diagnosis by tens of percent, as multiple studies (1, 2) show in human genetics.

In EquineTest, we offer data reanalysis once a year to keep up with newly discovered genetic markers. You do not need to perform additional tests or take new samples, as with whole genome sequencing, your horse’s genetic information remains a lifelong source – continuously revealing new information as science advances.