Recently I published a post warning owners about commercial companies offering unvalidated genetic testing for PSSM2 and other myopathies. This does not apply to PSSM1, which is a disease caused by an identified genetic defect that causes episodes of exertional rhabdomyolysis or “tying-up”. A validated commercial test exists for identifying the genetic defect that causes PSSM1 – the GYS1 mutation.
This post caused some vigorous discussion, including contributions from the founder of one of the companies. Unfortunately, these contributions were not helpful and did not provide any new insight and the person in question refused to answer direct questions about validation.
I stand by my comments that at this time, the genetic tests being offered commercially for PSSM2 and myopathies other than PSSM1 have not been subjected to independent peer review, nor data made available in the public domain on which to form an opinion as to the accuracy of these tests. At this time, these tests are UNVALIDATED. We do not know if they are accurate or not.
To further help those who may be confused or find this difficult to accept, here is a link to a document produced by Prof Richard Piercy from the Royal Veterinary College, London.
and some direct quotes….
“It can be very tempting when your horse has signs that might suggest a muscle problem to seek any answer you can find, particularly when the problem is proving challenging to diagnose and manage.”
“It might be even more tempting to believe an unsubstantiated genetic result when it ‘fits’ with what you have suspected. However, we encourage people to use an evidence basis to decision making when diagnosing these conditions and take into account the information presented above.”
“Until results of genetic testing for PSSM2 and other myopathies in horses are presented in peer-reviewed, validated scientific literature that is accepted by the scientific community (as has been the case for PSSM1), we do not recommend their use and certainly do not support veterinary or life decisions being made based on their results.”