Direct-to-consumer (DTC) genetic testing services have exploded in popularity in recent years thanks to companies like 23andMe and AncestryDNA. Once limited to estimates of familial lineage, more and more new DTC products promise to inform customers about their likelihood of developing major diseases and health conditions. Yet as numerous recent studies and investigative reports have revealed, the results of these analyses range from somewhat inaccurate to downright misleading.
The problem lies in the fact that the risk estimates are based not on whole genome sequencing, but rather the presence or absence of just a small number of gene variants that have been deemed ‘disease-causing’ because they turned up in the DNA of a few individuals with the condition. In reality, diseases are largely mediated by changes to multiple genes, and we simply don’t know the effect most of these variants have.
In April, a group of geneticists showed that DTC findings from multiple companies misidentify risk factors for disease about 40 percent of the time, falsely alarming customers about certain illnesses. At the same time, true susceptibility is overlooked because none of the available tests screen for all known disease-linked mutations.
Now, the rapidly expanding DTC industry has a fresh market: companion animal health tests. But as a trio of Harvard University veterinarians and geneticists warned in a Nature News commentary this week, these tests are plagued by the same issues; and drawing conclusions from them could be endangering beloved animals rather than helping them.
“Pet genetics must be reined in,” the authors wrote. “If not, some companies will continue to profit by selling potentially misleading and often inaccurate information; pets and their owners will suffer needlessly; and opportunities to improve pet health and even to leverage studies in dogs and cats to benefit human health might be lost. Ultimately, people will become more distrustful of science and medicine.”
According to their research, at least 19 laboratories are now marketing about 200 pet DTC tests – mostly for dogs – that cover 100 different diseases. The majority of the canine analyses are based on variants that have been flagged by just one candidate gene study. And because the data from these sequencing studies are typically not made public, other veterinary geneticists are unable to confirm or refute whether the variant is pathogenic in follow-up investigations. Considering that more than 98 percent of potential disease-causing variants identified in candidate gene studies are struck down by more advanced analysis, the chance that these tests accurately gauge your pet’s health is infinitesimal.
But concerned owners and even some veterinarians (the authors note that a major veterinary hospital chain is now recommending genetic testing for all dogs) are unaware of the many shortcomings of current personalized genomics technology. Illustrating the serious implications misguided faith in such tests can have, the article describes how a 13-year-old pug was put down after a DTC report suggested she had a progressive neurodegenerative disease. However, the mutation this dog carried is actually quite common, and as few as 1 percent of animals with it develop the disease.
Moving forward, the Harvard team calls for tighter regulations and quality standards, potentially enforced by agencies like the US Food and Drug Administration and the European Medicines Agency. They also urge all groups performing companion animal gene sequencing to begin sharing results in open-source databases that are managed by bioinformatics experts, as many human geneticists do. Finally, they emphasize the need for trained genetic counselors who can help pet owners calmly and logically interpret test results.
“In the United States alone, some 70 percent of households own pets. Done right, the use of genetic testing in companion animals could be a powerful way to better connect people to the possibilities of genetics for treating disease.”
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