HGTD - What is a Breed Relevance Rating?
To better support dog owners, the veterinary community, and dog health advisors, in 2020 we introduced Breed Relevance Ratings in the HGTD.
Below you will find an explanation of what the Breed Relevance Rating (BRR) is and why it is important. A work in progress... the BRR is a dynamic index that may change as new information becomes available.
To summarize the HGTD database relevance rating indicates the level of available evidence supporting the application of a specific genetic test for a specific breed/type.Currently, the relevance rating is based on a wide variety of evidence sources. This includes peer-reviewed research papers, recommendations from the original researchers/test developers, input from additional experts including veterinary specialists, and breed experts. It is hoped that, by being more informative about what we currently know or do not know about a specific test for a specific breed, that dog health advisors and owners can make more informed decisions. Remember, this Breed Relevance Rating is not everything we need to know about the disease or characteristic; it is focused on the genetic test.
Table of Contents
A description of the Breed relevance ratings is shown below:
Direct-to-consumer genetic tests have provided greater access to many different breed-specific and general genetic tests for dogs. This has raised concerns from owners and breeders who need more guidance and direction in making informed testing decisions. To help with this, the HGTD database includes a simplified rating, indicating the amount of available evidence supporting the relevance of a specific genetic test for a specific breed/type.
It is important when considering the ratings to understand that this effectively indicates how much we currently know or do not know about a specific test for a specific breed. This BRR pawprint rating does not necessarily indicate how “good”, or “bad” a test is. It also does not indicate the clinical importance of a test.
More information on the HGTD Breed Relevance Rating (BRR) - terms, application, and guidance
Different Test Types Definitions:
Genetic Disease/Disorder – relating to a disease, condition, or disorder. The results of a genetic disease/disorder test may indicate something about the risk or impact on the individual dog’s health and/or have health implications for future generations (e.g. can be used in breeding decisions). Common examples include inherited eye diseases and neurological diseases.
Other Genetic Traits – describes a broad category of attributes or traits that do not primarily have a health implication. The results of an “other genetic traits” test are most often indicating likelihood of a dog’s phenotype (how it looks) or phenotypic implications for future generations (e.g. breeding choices). Common examples include coat color, coat texture or length, or coat pattern.
Diagnostic Tool – describes genetic tests that are used to identify (rule in/rule out) a suspected condition, usually when an individual dog is exhibiting clinical signs, or may be used to indicate some risk or impact primarily on dog’s current health. May also have implications for breeding decisions, but more often used as a tool to confirm a diagnosis or predict health risks for an individual dog.
Parentage/Kinship/Identity/Scan – a broad category of genetic tests that generally are not directly related to health, but describe an individual dog’s relationships, or breed/type heritage. Also includes forms of permanent genetic-based identification based on the individual and/or confirming its sire and dam. Used by registries or in forensics.
What does it mean when there is a BRR for "ALL"?
Most tests were originally developed and offered for specific breeds. With the advent of panel testing, many Genetic Test Providers (GTPs) now offer some/many tests for 'All' dogs. Understandably, relevance may not be the same across all breeds. Where a BRR is assigned for "ALL" it is taking into account the research/relevance as it refers to dogs as a whole - breeds, crosses, and mixed dogs. Where the BRR is known to vary across breeds, the BRR may be assigned a yellow "unknown..." to indicate no consensus. If there are breeds within the "All" where the BRR would indicate that the test should not be used or is irrelevant, the "All" may be assigned an orange, "warning/caution" to indicate that there is no consensus, and usage in some breeds or types may be disadvantageous. Any green, "relevant..." BRR normally indicates a test that is understood to be universal across all dogs - such as genetic identification or parentage. It is important to note that where there is research/information for the test within a specific breed, that test will generally be listed as a breed-specific test, not simply under 'additional tests for All Dogs".
What is considered when estimating BRR?
The BRR rating is described as being an estimation. This best reflects the possibility that BRRs may change over time, as more evidence emerges and there is better understanding of the likely relevance of the test.
Currently there are around 2,500 combinations of specific breeds x specific test. Each of the genetic tests has to be considered on a breed-by-breed (or type) basis. While a test is waiting to be reviewed, it is assigned a "yellow" BRR, as it is considered "not yet determined". A breed may also have a yellow BRR for a test that is very new, still in a research phase, or where all current evidence indicates that relevance is unknown. Over time, the number of yellow BRRs should decrease. Any red, orange, or green BRRs arise from an evaluation of peer-reviewed scientific papers and consultation with experts - where possible including the original researchers behind the mutation discovery, as well as, additional geneticists, veterinary experts, and breed specialists.
A test is normally considered to have achieved a lowest-level green BRR when it meets some basic levels of relevance to a breed/type. If there is a peer-reviewed paper, it should make a correlation between the mutation tested for and the description of the clinical disease/phene in the specified breed, at a minimum. This rating should give the user some confidence that the mutation being tested for should be relevant to the breed. The green ratings get "stronger" as the strength of evidence increases; e.g. for genetic disease/disorder tests the likelihood of the mutation being causal increases, as there may be additional research, genetics expert information, larger dog populations tested, mutation frequencies estimated, evidence that using the test reduces the disease, etc.
The reverse is true as well. If a test is available and there is evidence that the mutation being tested for is not causal for the disease/phene, or even that using the test may give false or inaccurate results or is simply not recommended by the original researchers for testing in the breed, then an orange or red BRR could be assigned. For example, in some breeds it is possible for the mutation to exist in the breed, but it has been demonstrated repeatedly that for some reason the mutation does not cause the condition being tested for, and/or the disease/condition has never been reported in the breed.
How do BRRs apply to my Breed?
The BRR is an estimate of the currently known research and understanding of a disease/phene as it applies to specific breed(s)/types. If you are considering using the BRRs as a breed club, health adviser, or veterinary professional, one practical way to interpret it is as a scale of prioritization. For example, if a test has a green BRR rating of any level, it has likely been established that screening for this disease/phene is reasonable, and the results are relevant and could be used in breeding plans or strategies. A yellow BRR test may or may not be relevant, so finding out more about the test could be important in deciding if it's appropriate or should be prioritized. Orange and Red tests indicate that there is a recommendation of caution from the research community, and the test may not be applicable to the breed. However, it is important to be clear that the BRR applys primarily to the use of the genetic test, per se, and do not fully address how important the disease or characteristic being test for is relative to other conditions which should be considered in breeding decisions! Information on genetic tests and testing must be considered as just one tool in the full context of health in the breed.
How do BRRs apply to my dog?
The BRR is an estimate of the currently known research and understanding of a disease/phene as it applies to specific breed(s)/types. Which tests should be prioritized for an individual dog, or how important a test result may be will vary depending on other factors - such as differences in global breed populations, individual dog risks (e.g. if a family member has a disease being tested for), and the reasons for testing (e.g. diagnostic, breeding plans, general screening...). No permanent or irreversible decision should be made about a dog based on a genetic test result alone. It is important to discuss any concerns with a veterinary professional and, if possible, a canine genetic advisory. Some/many genetic tests apply primarily to breeding decisions and have no real impact on or meaning for the individual dog in its lifetime.
Breed Relevance Rating ???'s - Input?
If you are a researcher or other expert, and believe a rating is inaccurate, or if you have data or test information you would like to share, please contact email@example.com.