John D. Loike, a Professor of Biology at Touro College and University Systems, writes a regular column on bioethics for The Scientist.

Direct-to-consumer DNA testing has provided genetic information to more than 12 million individuals, traditionally for exploring ancestry. While such testing does not violate ethical guidelines, other uses of consumer DNA testing may cross the line. Over the past few years, many of these DNA testing companies have branched out into the realm of precision health, treading into ethically dangerous territories. 

For example, 23andMe, with US Food and Drug Administration (FDA) permission, now reveals to consumers whether they possess a whole suite of genetic mutations, including those associated with Lynch syndrome and breast cancer, under the assumption that awareness will likely improve the health of its consumers. Other companies advertise that their DNA testing will better educate customers on what type...

The major problems with these tests are two-fold. First, many of the tests lack scientific validity to support the genetic outcomes revealed to their customers. Not all of the 25 major companies engaged in direct-to-consumer DNA testing have been Clinical Laboratory Improvement Amendments certified. Second, there is no professional counseling required before and after the consumer receives her results.

A single telomere test, even when it is highly accurate, can’t provide a true picture of biological aging because what is important is how fast the telomeres are shortening.

For example, companies such as Vitagene, TeloYears, and 23andMe use DNA testing to assess a person’s health and/or longevity. Vitagene claims that its product helps individuals choose which vitamins are most appropriate for their bodies and will even sell a personalized “optimum” vitamin regimen for $79/month. TeloYears measures telomere length in blood cells “to help you stay younger longer.” Helix informs their clients their athletic abilities, diet, and sleep patterns. 23andMe claims to inform the customer about recessive genetic variants that may not affect their health but could affect the health of their children.

The lack of context attendant with consumer DNA testing for health reasons is a serious and potentially harmful issue. 23andMe, for example, only tests for three of the most common BRCA mutations associated with an increased risk of getting breast cancer. In fact, there are almost 1,000 BRCA mutations that need to be assayed to provide an accurate assessment. In addition, not all of these mutations are deleterious because there are other gene variants that an individual may carry that mitigate the risk for breast cancer. 

In one small study, Ambry Genetics examined 49 samples sent in by physicians whose patients had been told that they had disease-causing mutations by a third-party vendor. Ambry Genetics found that 40 percent of the results were wrong. In addition, some genetic variations classified by these companies as threatening were actually benign. The problem is that the customers think they are getting the same kind of precision genetic testing that they would get from a certified clinical laboratory.

The idea of measuring telomere length to estimate longevity has some scientific merit. There are studies and patents that provide methods of determining human telomere length and correlating shorter telomeres with an increased mortality rate and increased susceptibility to certain types of conditions, such as cardiovascular disease. Moreover, unhealthy lifestyle factors, such as smoking, junk food, obesity, inactivity, and chronic stress, all are associated with shorter telomeres. However, there is a wide range of “normal” telomere lengths. Scientists have shown that cells don’t trigger apoptosis unless telomeres get extremely short. In addition, many consumer companies use quantitative polymerase chain reaction to assess telomere length. This test has a 20 percent variability rate and sometimes testing on different days can yield different results. In contrast, clinical labs typically use flow cytometry and fluorescent in situ hybridization to measure telomere length, a protocol that has a lower variability rate (5 percent). Equally important is that a single telomere test, even when it is highly accurate, can’t provide a true picture of biological aging because what is important is how fast the telomeres are shortening. To determine that rate, a baseline test must be followed up over time by other tests, something these consumer labs do not generally do. 

Equally disturbing are the companies advertising DNA tests designed to inspire their consumers to develop more personalized diets, workouts, and supplements, often with the overall goal of weight loss. There are no published scientific data that support the idea that current genetic testing can help design a bespoke diet that will benefit one’s health. In fact, the few studies published show absolutely no connection between existing DNA testing and choosing the best diet to lose weight. Further, scientists have not identified a general “overweight gene,” although hundreds of weight-associated genes have been identified in genome-wide association studies, including a few rare obesity genes. 

Aside from the accuracy problem, revealing these genetic results to customers may pose serious psychological and medical ramifications. In my experience, the public does not really understand the complexities of genetics and epigenetics in predicting disease onset or severity. Will customers whose DNA testing reveals a deleterious mutation seek out a consultation with a certified genetic counselor? It is also unclear how many clients will seek medical advice after receiving news that they carry a genetic disease. Conversely, if customers are told they have no breast cancer risks, will this information lead them to forgo recommended cancer testing, such as mammograms, as they age? Testing companies such as 23andMe say they are not at fault, because they make it clear that their data are not meant to be used for medical diagnoses. Why then provide such elliptical information to the uneducated consumer?       

Understandably, many people want to know about their health or longevity without making that information available to insurance companies for fear their insurance rates will go up. Yet, consumer DNA testing companies offering gene health tests promote an illusion of private, personalized medical information under the aegis of empowerment. However appealing that may sound, the truthfulness and utility of these tests are not obvious. Who really benefits from such testing?

The complexity of genetics and disease risks mandates an ethical directive that customers requesting such tests should also require genetic counseling and education, both prior to doing the tests and after receiving their results. DNA testing for health by clinically certified laboratories is the only logical way to proceed. Only certified geneticists should be presenting genetic results to consumers and patients in a comprehensive manner that reduces the medical and psychological repercussions of either positive or negative data. The same reason why certain drugs require a physician’s prescription sets a precedent that DNA testing requires a physician’s supervision. While medicine is heading towards precision care, direct-to-consumer DNA testing companies are crossing into unethical territories by not yet providing precision health information. Therefore, the FDA should warn the public of the potential harm in using these DNA tests for medical reasons and doctors should discourage patients from taking them until the science has improved.

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