Probability Theory and Medicine


“Hypothetically speaking, let’s say you get your genome sequenced and the report says that you have a genetic mutation. What is your interpretation of your report?”

Well, if you ask a biologist this question, they would probably counter question you with a million other questions: “Which gene do I have a mutation in? What is its function? Does it code for something that will have a phenotypic expression like eye color or does it code for a protein that will affect important functions like apoptosis?”

What would a statistician say? Well, after knowing all the facts about gene expression and function they would probably explain: “Whether you are buying a lottery ticket or flipping a coin or standing near an electrical conductor during heavy rains, there is a miniscule chance of winning the lottery, landing a heads/tails 10 times in a row in a coin flip or getting struck by lightning. So if I have a mutation in this gene, what are the chances that I would get the disease?”

Well, for the following situation I think we should all have the statistician’s viewpoint. Recently, the FDA banned 23andMe from offering health reports that guide the consumer through an interpretation of their sequenced genome citing “misguided responses” from the public as a reason.

But, is the way the consumers interpret the results really the company’s fault? One of the reasons for the ban, which the FDA mentioned in their warning letter addressed to 23andMe founder Anne Wojcicki, was that the personal genomic services offered by 23andMe may provide false positive results leading to unnecessary medical interventions or, in case of false negatives, overlook serious medical conditions. This battle between the FDA and 23andMe has raised one of the liveliest debates in medical ethics today.

The first concern of every medical innovation is its interpretation in terms of public health usefulness. In case of 23andMe’s personal genomic services it’s about how the user interprets the health reports that are provided based on their genome sequencing. The fact that we are living creatures on planet Earth opens us up to this Pandora’s box full of maladies. But, would you like to know which of those miseries might lie in your future?

The thing that most people don’t realize is that getting your genome sequenced will only tell you about the diseases that you are at risk for. It doesn’t tell you definitively whether you will have a disease in the future or not. Nobody can tell you that. It is all about probability.

Every human is born with about an average of 100 mutations in their genome. Yes, each and everyone one of us! Based on this information shouldn’t we all develop some sort of disorder at some point in our lifetime? But, most of us don’t. All of us are living breathing proof of the fact that we can live a long healthy life with mutations in our genome.

Environmental factors play a very important role in disease presentation from a genetic predisposition. Drugs and chemicals in our environment have been shown to affect gene expression.

The health report that 23andMe offered prior to the ban described the risk factors associated if a gene was found mutated in the genomic sequence. But genes are indirect actors; genes have to be translated to proteins to cause any actual health affect. There are countless factors involved in gene expression. For example, the way that the 3 billion base pairs are condensed and packaged into every single cell can affect gene expression.

Based on a genome sequence, there is no way of knowing with a complete guarantee if you are going to get a disease or not, there is only a probability.

If you ask me, yes, I have a right to know the medical translation of the document that is my genome if I choose to! But, I say this as a researcher, a person who has some knowledge of genetics and how genes work.

But people who are not well versed in genetics are probably going to grasp knowledge from publicized confessions of celebrities describing grandiose medical interventions to genetic testing as the only possible solution.

So, maybe the FDA, or for that matter 23andMe, are not the ones to be blamed, but the media is for creating a flawed narrative with more column inches spent on sensational stories than on actual scientific critique.

So, let me ask you this: Should our DNA be our destiny? Are we putting too much pressure on the 3 billion letters to define our future health?



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