What a DNA health panel actually tests for

"DNA health tested" is one of the most reassuring phrases in a puppy advert, and one of the least specific. A breeder who uses it may mean a single-condition test bought online for the price of a vet visit. They may mean a twenty-condition breed panel run through a specialist genetics laboratory. They may mean something in between. The phrase carries none of that distinction, and the buyer reading it has almost no way to tell which one they are looking at.

This is the companion piece to what a hip score actually tells you and what a coefficient of inbreeding actually tells you — both about reading a specific number correctly once you have it. This one is about reading a claim correctly, because "health tested" is doing a great deal of unexamined work in most adverts, and the gap between what it could mean and what it usually does mean is wide enough to matter.

Clear, carrier, affected — and what each one actually commits a breeder to

Three words carry almost the whole weight of a DNA health-test result, and they are worth being precise about, because breeding decisions turn on them.

Clear means the dog carries no copies of the specific mutation tested. Bred to another clear dog, or in most cases to a carrier, it cannot produce a puppy affected by that particular condition.

Carrier means one copy of the mutation and one normal copy. A carrier dog is not expected to develop the condition itself. Responsible breeding practice — and most breed club codes of ethics — permit a carrier to be bred, but only to a dog confirmed clear for the same mutation, which keeps affected puppies out of the litter even though roughly half the resulting puppies will themselves be carriers.

Affected means two copies. For a recessive single-gene condition, which is what most DNA panels test for, the dog will develop it, sometimes early, sometimes only later in life depending on the disease. An affected dog can still be bred, carefully, to a clear partner, producing an entire litter of carriers and no affected puppies — whether that is wise depends on the condition, the breed's gene pool, and advice from a vet geneticist, not a blanket rule.

None of those three words is a verdict on the dog as a companion. A carrier, or even an affected dog, can live a full, comfortable, much-loved life outside a breeding programme. The words describe breeding risk for one specific mutation. Nothing more.

The part that catches buyers out: the panel is not the breed

Here is the gap "DNA health tested" hides. A Border Collie panel and a Labrador panel are not the same list, because the two breeds carry different inherited risks.

A Border Collie panel typically screens for conditions including Collie Eye Anomaly, Trapped Neutrophil Syndrome, Neuronal Ceroid Lipofuscinosis, and the MDR1 drug-sensitivity variant, which affects how a dog metabolises certain common medications, ivermectin among them. TNS carrier rates in the breed have been estimated at 10 to 15 percent worldwide, which is part of why breed clubs treat testing for it as close to routine rather than optional.

A Labrador panel typically covers a different list entirely: Centronuclear Myopathy, the prcd form of Progressive Retinal Atrophy, the D-locus dilute-colour variant, and — depending on the lab and the package a breeder buys — Exercise-Induced Collapse and Hereditary Nasal Parakeratosis as separate add-ons rather than standard inclusions.

Neither list is wrong. Both are appropriate to the breed they cover. But "DNA health tested" said about a Border Collie and the same phrase said about a Labrador describe two entirely different sets of conditions, tested through what may be two different laboratories at two different levels of rigour — and a buyer comparing litters, even of the same breed from different breeders, is very rarely told which conditions were actually on the list.

The useful question to ask a breeder is not "is she DNA tested?" but "tested for which conditions, through which lab, and can I see the certificate?" A breeder doing the work properly will produce that certificate without hesitation, because it is the only version of the claim that actually means anything.

"Clear by parentage" is a real category, and a narrower one than it sounds

A puppy can be marked clear for a condition without ever being tested itself, provided both parents were tested clear for that same specific mutation. This is called clear by parentage, and it is a legitimate, widely used shortcut — two clear parents cannot, for a straightforward recessive condition, produce an affected puppy, so retesting every puppy in the litter is redundant.

It is also narrower than it sounds on an advert. Clear by parentage covers exactly one disease mutation, confirmed through exactly the parents named — not the grandparents, not a littermate, not the same condition tested by a different method. A puppy correctly described as clear by parentage for one condition can still be a complete unknown for every other condition on the relevant panel. And the designation depends entirely on the parentage being correctly recorded, which is why registries increasingly pair it with a separate DNA parentage-verification test rather than taking the stud book's word for it.

The Royal Kennel Club tightened its own version of this in 2019, limiting how many generations a "hereditary clear" status could be inherited down a pedigree without fresh verification. The change followed research showing that a single incorrect result — a laboratory error, a mis-recorded mating — could propagate a false clear status through several generations of apparently low-risk breeding before anyone noticed it. The fix was procedural rather than dramatic: cap the inheritance at two generations unless the parentage itself is DNA-verified. It is a good illustration of how far downstream a single test result can travel, and why "her line has always tested clear" is a considerably weaker claim than "here is her own certificate."

What we ask for, and why the lab and the panel both matter

On a GenoVaq listing, a health-tested claim is not a badge. It is a specific set of fields: which conditions, through which laboratory, clear, carrier or affected against each one, and the certificate itself where a breeder is willing to share it. Two dogs both marked "DNA health tested" can look identical as a badge and turn out to be completely different once the actual panel is visible — and the difference is usually the whole point.

This will not tell a buyer everything. It will not replace the structural screening covered in what a hip score actually tells you and what an elbow grade actually tells you, which test conditions no DNA panel can see. It will not replace the population-level thinking in why rare breeds don't breed the carriers out, which is about managing a breed's whole gene pool rather than one litter. But it turns a two-word reassurance into something a buyer can actually check, against a certificate, before they commit to anything.

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Sources

• Royal Kennel Club — understanding and using your dog's DNA test results
• Royal Kennel Club — "Kennel Club limits 'hereditary clear' status", September 2019
• UC Davis Veterinary Genetics Laboratory — Border Collie Health Panel
• BCCNSW — Trapped Neutrophil Syndrome (TNS)
• American Kennel Club — Labrador Retriever DNA Tests
• American Kennel Club — Clear by Parentage: What Dog Breeders Need to Know

— Rene