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Accuracy: Direct Versus Indirect Genetic Testing

By February 5, 2024No Comments

When thinking about genetic health and coat testing, there can be several factors that influence a person’s decision but accuracy is almost always at the top of the list. Many factors can influence test accuracy, with the first and most important being the mutation being detected. Unlike breed testing, when it comes to health and coat testing and assuming good laboratory procedures, you should get the same result regardless of which laboratory you use. However, there are certain situations where you may not get the same result and it has nothing to do with the level of laboratory competence. It’s because surprisingly, not all laboratories test for the same mutation when it comes to certain diseases or coat tests.

When doing any type of genetic testing there are two ways to test for a mutation known as direct and indirect testing. Direct testing is straightforward and determines the presence of the mutation scientifically demonstrated to cause the disease. This allows a direct connection to be made between a test result and what you can expect to see in the dog. Direct testing is by far the best method when you want the most accurate result possible. There can be situations where direct testing is not feasible for a particular laboratory and that’s when they will use the second method known as indirect testing.

Indirect testing (also referred to as linkage testing) is a process of looking for mutations that are near the disease-causing mutation and most of the time signal the presence of the disease-causing mutation. The problem is that due to a biological process known as recombination, the indirect mutations can become physically separated from the disease-causing mutation and can give a false result. Since this does not happen when using direct testing, this begs the question why would a laboratory use indirect testing if it’s less accurate? The first reason is that the actual disease-causing mutation has yet to be discovered. When research scientists are first trying to find the mutation that causes a genetic disease, they first start by narrowing down the general area of the genome where the mutation is likely to be. During these earlier phases of research, indirect testing can be used as a guide to which dogs will suffer from the disease but does not provide the whole picture. As the research develops further, the causative mutation is often located and the test is then converted into a more accurate direct test. So, sometimes indirect testing is used as a temporary option until more information becomes available.

The other reason indirect testing is used is because the testing technology used by a laboratory may be limited in its ability to detect certain types of mutations or the tests developed by the laboratory can’t be designed to detect the precise causative mutation. So, the laboratory will use indirect testing due to technical limitations. Some examples of indirect tests offered by other laboratories include Chondrodystrophy and Intervertebral Disc Disease (CDDY/IVDD), Furnishings (Imperfect Coat), I-Locus (Intensity), Hairlessness (FOX13) and potentially others. Similar to using indirect testing due to early phase research, these tests can only reach a certain level of accuracy but they can never be 100% accurate because in both cases you are not detecting the disease-causing mutation. Unfortunately, when using indirect testing there will inevitably be cases where the test result is incorrect. This can lead to inadvertently maintaining a disease or unwanted coat mutation in a breeding program and even producing pups with the disease or unwanted coat. This is why, when the actual mutation is known, the best and most accurate form of testing is always direct testing.

That’s why at GenSol, every test we offer is done by direct testing which only detects the mutation known through scientific research to lead to the disease or coat. We believe that making good breeding and health decisions starts with the most accurate results possible. And the most accurate results start with testing for the correct mutation. Although indirect testing is a part of the research process, we don’t believe it should be part of the diagnostic process once the causative mutation is known. We don’t offer indirect testing found in early-stage research. Our technology allows us to test for any type of mutation as opposed to other companies that are limited by their technology and compromise with indirect testing. We use science and innovation to deliver the most accurate results possible so you can make the best decisions. Make sure you check with your genetic test provider to determine what type of testing they do and don’t hesitate to contact us if you have questions.