Negative screening for HCM in Maine Coon kittens does not rule out the disease

In layperson's terms, we know that it's possible to screen Maine Coon breeding cats, foundation cats and the parents of kittens plus the kittens created at cat breeders for hypertrophic cardiomyopathy in order to prevent the creation of Maine Coon cats who are predisposed to hypertrophic cardiomyopathy (HCM) and therefore to reassure purchasers of purebred Maine Coon cats that their purchase will not show signs of the disease quite soon after purchase and have a shortened lifespan as a consequence.

By 'screening' I mean testing for a mutant gene that causes the disease.

When a Maine Coon breeder says that they screen their cats and kittens for the disease that they sell to clients, should a negative test result totally reassure the client that their purchased kitten will not develop HCM? That is the $64,000 question.

The answer to that question is clearly NO, sadly. My research clearly indicates that a Maine Coon cat screened as negative for HCM may still develop this heart disease because there are other currently undiscovered genetic mutations that can cause the disease. The information comes from the Universities Federation for Animal Welfare.

And the same information comes from a veterinary clinic/facility with a big online presence for carrying out screening for HCM. They are called Langford Vets in the UK and they say this about screens HCM in Maine Coon cats:

The Molecular Diagnostic Unit can now offer genetic testing for hypertrophic cardiomyopathy in Maine Coon and Ragdoll cats. We have developed PCR assays to quickly and accurately identify the two MYBPC3 gene mutations currently linked with HCM in Maine Coon (A31P) and Ragdoll (R820W) cats. 

Comment on the above: they are saying that they have a molecular diagnostic test to detect two genetic mutations linked to HCM. If those mutations are not present then the cat is not predisposed HCM. That's the argument.

But they go on to state that, "[There maybe] as yet unidentified, genetic mutations [which can) also cause HCM or modify the risk".

They further add that, "A normal result on the Maine Coon HCM genetic test means that the cat does not have the genetic mutation [referred to above]. It is possible that some cats may go on to develop cardiac disease due to other, as yet unidentified genetic mutations."

Comment: It seems to me that the fact of the matter is that researchers are still identifying the genetic mutations causing hypertrophic cardiomyopathy in Maine Coon cats and other cats. This is the most common heart disease in domestic cats generally including non-purebred cats.

This is work in progress. They have identified some genes which cause it as mentioned above again. But this, clearly, is not the complete story which is why the answer to the question in the highlighted sentence above is that a purchaser cannot be certain that their kitten/cat will not develop HCM despite being screened by the breeder and the result coming back negative.