AVCG.

Why the AVCG exists

Human medicine agreed on how to read a variant. Animal genetics had not.

When a human geneticist finds a variant and needs to say whether it causes disease, they do not guess. They apply the ACMG/AMP guidelines: a shared, criteria-based rulebook that weighs the evidence and lands on one of five verdicts. The point of it is reproducibility. Two qualified people looking at the same variant and the same evidence should reach the same call. That agreement is what makes a classification trustworthy rather than an opinion.

Animals had no equivalent. A variant called disease-causing by one laboratory might be called uncertain by the next, because there was no common standard for how to decide. The same problem OMIA solved for cataloguing inherited disease, scattered knowledge with no shared home, existed one level down, in the act of classification itself.

The Animal Variant Classification Guidelines are the answer. Published in 2024 by Boeykens, Broeckx and colleagues at Ghent University, they adapt the human standard for animals: the same five-tier scale, the same idea of weighing defined categories of evidence, tuned to the realities of animal genetics. For the first time, a canine, feline, or equine variant can be graded by an objective, published method instead of a judgment call.

How the AVCG works

The AVCG applies to single-gene disorders: conditions where a variant in one gene has a high enough impact that one variant is sufficient, though not always fully penetrant, to cause disease. For such a variant, the guidelines ask a set of evidence questions. Does it change the protein in a damaging way? Does it track with the disease across affected animals? Is it absent from healthy populations? Has a functional study shown an effect? Each answer adds or removes weight, and the accumulated weight lands the variant on a grade.

What the AVCG contributes to Sniff

Every pathogenicity grade on Sniff is an AVCG classification.

When a disease page shows that a documented variant is pathogenic, that grade was assigned under the AVCG and curated in OMIA. Sniff does not invent grades and does not score these variants with its own model. It reads the published classification and shows it, with its source. The AVCG is the rulebook; OMIA is where the resulting calls are recorded; Sniff is the surface that brings them together and makes them readable.

The classification table is the AVCG layer made queryable. Every graded variant we hold across dog, cat, and horse, on one page, each with its species, disease, the exact variant in HGVS, the reference genome, and a link to its OMIA entry. The grades are deliberately sparse, because a real classification takes evidence that often does not exist yet, and that sparseness is the honesty of it. We are adding the per-criteria detail behind each call, the specific evidence that fired, from the open-access guideline supplements, along with a corroboration record toward reproducibility.

It is the difference between a site that grades a variant by guesswork and one that shows you a published, reproducible classification and points you to where it lives. We chose the second kind.