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01/08/2014

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Genetic tests for the public: are they worthwhile?

Christine Hauskeller and Cecile Janssens disagree

Dear Cecile,

Many argue, as you do, that publicly available genetic tests do not benefit buyers concerned about their personal risk of common diseases such as diabetes or stroke. Genetic tests are not ready for an open market, the argument runs. The matter is too complex and the science not advanced enough.

I suggest that buyers derive good value from home health testing. Most importantly, they can gather information before seeing a physician. Well-prepared, well-informed patients fare better and are more satisfied with the outcome of consultations.

Consumers, it is argued, may be tricked into buying products without benefit. They may worry unnecessarily (or not enough) about their risks and lifestyle. And invalid tests may taint the reputation of genomic knowledge, at a time when the genetic contribution to complex diseases is not readily understood.

But why these concerns, given that many useless or harmful products are sold? We should assume that most buyers are aware of the limited validity of the tests. Given all the hype about and public investment in genetics, it seems only fair that the fragility of most current genomic knowledge is communicated publicly, on blogs and the internet pages of genetic testing companies, rather than keeping it an expert secret.

Regards,

Christine

Dear Christine,

I have also noticed that people want to decide themselves whether a test benefits them, and who am I to say it does not? Yet, I cannot believe people still see benefits when they understand the limited predictive ability of the test. Take, for example, the home pregnancy test.

The home pregnancy test has very high predictive ability. If it tells you’re pregnant, you are. And if it tells you’re not, you’re not. That is very useful information – if you think you might be pregnant, of course. You can visit your GP to ask for prenatal vitamins or for an abortion, for example. It’s great that such a highly predictive test is available in drug stores for home use.

But what if the test were not so predictive? What if it told you that you had a 55 per cent probability of being pregnant? And that, when you took the test again two days later, the probability was 40 per cent instead of 55 per cent? What question would you ask your GP? Would you still feel well-prepared and well-informed? That is about the current validity of the publicly-available genetic tests for common diseases. Do you still see benefits of taking the genetic test?

Regards,

Cecile

Dear Cecile,

I believe that what is helpful is best known to the person who feels helped. Yet, I agree, the problem with the direct-to-consumer genetic tests may be that too much is promised at present. A survey among clinicians found that these tests were seen as helpful in alerting unsuspecting patients and their physicians to predispositions to hereditary breast cancer. Where the genetics is rather well established, the tests may work.

To reach a wide market, the tests include profiles for common diseases. You seem to argue that, as long as prediction for specific diseases is not more reliable, marketing is premature.

But the market has developed and is unlikely to disappear. I therefore suggest developing a scientifically and ethically sound system of certification for direct-to-consumer genetic tests that would offer buyers informed product choices. Such a quality control system would take an internationally concerted effort, but could protect both the image of genetic science and the medical professions and health care system from the effects of poor quality tests.

Conversely, attempting to establish predictive value and responsible and ethical practice around genetic testing may highlight the vagueness of genetics for common or complex diseases and put at risk the public trust in the future delivery of genetic science.

Regards,

Christine

Dear Christine,

It is worrisome when clinicians see these tests as helpful in alerting unsuspecting patients. The tests have never been evaluated for that purpose and generally these success stories are only anecdotal. Even scarier is the idea that if clinicians do not understand the limited predictive ability of these genetic tests, how should we trust that they understand predictive ability at all?

I am not sure whether regulation is the solution here. It will be a challenge to develop standards and certificates for direct to consumer genetic tests, as genetic tests for multifactorial diseases are not intrinsically useless. Whether the predictive ability and utility are sufficient will depend on what you want to do with it and in which population, and this may differ from disease to disease. I do not easily see how we can capture this in clear regulation.

But I do not worry: if direct-to-consumer tests continue to have limited utility, consumer interest will remain limited and ultimately companies will disappear or change their activities to more profitable directions. Therefore, I think that we should focus on educating health care workers and the public so they understand the limited value and lose interest.

Regards,

Cecile

Dear Cecile,

Is it the nature of genetics to be valid for diagnostic use only when tailored to an individual? Then the promise of genetics will remain unfulfilled. Technologies dependent on personal application tend to serve only the rich and can hardly merit massive public funding support. The aim must be widespread applications. These do exist already.

Prenatal genetics, including testing for sickle cell disease, for example, has become a part of reproductive healthcare. Consumers may recognize that there are thousands of genetic markers related to breast cancer or sudden cardiac death and still find comfort in learning that they do not carry some of them, without expecting guaranteed freedom from these diseases.

While the ideal of science may be complete knowledge, most human practices operate with incomplete knowledge and uncertainty. Given the present state of genetic tests for common diseases, scientists would probably want to advertise them (with certain exceptions for individuals) as being as valid as reading the stars. Yet, even with this degree of uncertainty, the market can flourish.

Credibility demands enabling consumers to identify clinically valid and ethically sound tests. If the genetics of common diseases is too complex, tests containing such panels will go uncertified. That should shrivel the market for ineffective tests, and strengthen it for worthwhile ones.

Regards,

Christine

Dear Christine,

Consumers may definitely find value in learning that they do not carry mutations, like parents-to-be do in prenatal genetics. This is informative when most or the major mutations are covered. Yet, for breast cancer, 23andme tests only three of the thousands of mutations that have been identified in the BRCA1 and BRCA2 genes. What is the value of knowing that you do not have these three when you still may have one of the thousands others, or one of the who-knows-how-many that are still unknown? When discussing the utility of personal genome testing, it is important to check what is actually tested for.

For consumers, but also for health care professionals, it is confusing that DNA is very predictive and not predictive at the same time. And that even if it is very predictive, it can be useless to test. And that if it is not predictive and useful to predict risks at the individual level, as in personal genome testing, it can be good enough to predict disease and identify high-risk groups at the population level.

Explaining predictive ability and utility will remain an enormous and important challenge. And a necessity to prevent companies getting away with claiming personal utility when there is no medical benefit of testing.

Regards,

Cecile

Dr Christine Hauskeller
Dr Christine Hauskeller is Co-Director at the ESRC Centre for Genomics in Society (EGENIS) at the University of Exeter
Dr Cecile Janssens
Dr Cecile Janssens is Professor of Translational Epidemiology at the Erasmus University Medical Center in Rotterdam
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