The problem with personalized genetic testing

You send a sample of your saliva in to a company who promises to look up your risk for over 200 different diseases. You have been curious about your genetic health for a while now and want to know what things you may expect from your future years. The results are returned to you and you find out that you carry a mutation in the BRCA1 gene. Due to that mutation, you that you have a very high risk of developing breast cancer at some point in your future. What do you do now? How long till you get it? Will your daughter be at risk? What are your treatment options? How do you tell your family?

Personalized genetic testing has been on the market now for around 10 years. It allows people to send samples of their saliva to screen their genome for mutations or subtle variations that may increase their risk for certain diseases. This type of personalized testing has noble purposes:

  • Move medicine from reactive to preventative
  • Tailor treatments to your genetic makeup (personalized medicine)
  • Anticipate the development of disease for better treatment
  • Initiate lifestyle changes in people

There are, however, lots of problems with this type of testing that prevents it from being as useful as we all had initially hoped.

  • First of all, we don’t know enough about how all these genetic variations interact with a person’s environment to contribute to disease. Someone has a variant that increases their risk of developing heart disease but is this risk modified if they smoke? If they live by a highway? If they work in a stressful setting? What about if their siblings or parents had heart disease? Do they eat healthy? Do they exercise regularly? There are many environmental exposures that can modify whether or not you get disease and we cannot test for those with this kit. Without the input of a doctor, you cannot know if this gene variant will lead to any meaningful impact in your life.
  • Second, the risks associated with each variant can be very small. Your risk of developing heart disease if you have a certain variant may change from 7% to 9%. Is this big? No, if only 7 out of every 100 people develop a heart attack then having this mutation means only an additional 2 people would go on to develop heart attacks. Compare that to smoking where your risk of heart disease increases from 18-20% and you can see that the variation in a gene makes up only a small risk. The same thing goes for many of the diseases these kits test including: asthma, certain forms of cancer, Alzheimer’s, and blindness. There isn’t one variant that contributes completely to these diseases. Instead there are multiple variants that add up to increase your risk of disease and so testing just one of them doesn’t give a whole picture.
  • Third, the question of time. When will I get this disease? The test cannot tell you if it will happen tomorrow or in 40 years. People who fear that they are at risk for a terrible disease may live their life in fear, never knowing when they can except the disease to appear. Sometimes the disease may never appear.
  • Finally, without the guidance or counselling of experts, these results can lead to feelings of hopelessness for those with a risk for developing a terrible disease (Cancer, Huntington’s) or even a sense of invincibility for those who find out they don’t carry the mutation. For the example above, you find out you carry a variant in a gene that increases your risk of breast cancer up to 80%. Do you give up hope? Seek treatment? Have kids? What if you find out you don’t carry it, will you partake in risky behaviour because you feel invincible? What about for Huntington’s disease? If you carry the mutation do you have kids? When will you loose your mind? How will it impact your family? Without the proper support these results can become overwhelming.

2 years ago a company who offered this type of testing was banned from selling their kit to consumers because the FDA determined that the company had not proven that it had its tests were clinically relevant or important. Most of the 254 conditions that were part of the original kit did not have enough strong scientific evidence to link variations in specific genes to disease. Now, 2 years later, the company has released a condensed kit that only tests for 36 diseases for which there exists strong, clinically approved data and test. This includes tests for sickle cell anemia and cystic fibrosis. The company is now refraining from testing so called ‘high risk’ diseases like breast cancer and Alzheimer’s over concern how receiving that information may affect someone’s well being.

If one of these tests is performed with the company it is best that the results be reviewed with a doctor or genetic counsellor who can put them into context. Personalized medicine is on its way and certainly in the future we will know more about the genetic and environmental origins of disease to make tests like this more valuable. However, at this moment in time the kits don’t have enough scientific evidence behind them to make them a ground-breaking tool.

Here is a great article outlining in more detail the pitfalls and concerns with direct to consumer genetic testing like 23andMe.

Photo Credit: CDC Genomics and Health Impact Blog


One thought on “The problem with personalized genetic testing

  1. Julie had been checking out the faulty BRCA1 gene two years ago by genetic testing, which means she has 87% and 50% chance of developing breast and ovarian cancer. Her mother has been found with breast cancer, and eventually died of ovarian cancer once.

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