Genetic Risk Prediction: The Difference Between Diagnostics and Research

While I’m loath to disagree with ScienceBlogling Daniel MacArthur about genomics, I can’t really agree with his assessment of genetic risk prediction:

Wright provides a balanced review of the implications of the article, and finishes with a paragraph worth quoting verbatim:

However, far from supporting calls to forbid such tests being available DTC, this highlights the need for transparency</em in the provision of information.Companies offering genome-wide risk prediction services should ensure that their customers understand that, whilst the measurement of the DNA sequenceitself (the assay) will remain constant, the interpretation of the result (the test) is likely to change as the science develops.

Amen. As I have consistently argued here on Genetic Future, the solution to the alleged dangers of personal genomics is not banning the public from having access to their own genome (as Germany has recently done), or forcing them to seek permission from their doctor before peering into their own DNA. Instead, the answer is to ensure that companies provide at least the minimal information required for customers to make an informed decision about the utility of risk predictions, and to punish those companies who fail to do so with public censure and (if absolutely necessary) regulatory action.

To me, any test that yields either an increased risk or a decreased risk of disease depending on the analysis is not a test that should be used in medicine. This isn’t a quantiative difference (which would raise its own issues), but a qualitative one.
I can’t even begin to imagine the public health nightmare that would exist if we were to hold antibiotic susceptibility testing–how we determine if an antibiotic will work against a bacterial infection–to this same non-existent standard. While genetic risk prediction doesn’t have the immediate effect of failed antibiotic therapy, what if it leads to inappropriate treatment?
If it is an inaccurate medical diagnostic, then it should not be used. Because, like it or not, anything that says “genome” or “DNA” will be granted special status (look at the criminal justice system). Most MDs aren’t population geneticists or statisticians*–like most people, they want an answer that is robust**. Expecting after-the-fact regulation to be effective just isn’t realistic–if a diagnostic isn’t reliable, don’t release it as a diagnostic because it will be used.
I do think genetic risk prediction will be a useful tool. Will be. But I’m not sure that right now it’s where it needs to be. If we want rich guys who sequence their genomes to have fun, or if people, who want to advance medical science, are willing to be tested, that’s one thing. But a diagnostic is another.
*I’m not impugning the intelligence of doctors, but if you need to be an active researcher in this area to understand the limitations of the diagnosis, then it’s not ready.
**Apparently, robust has become a managerial-speak buzzword. I simply mean that the result is not hyper-sensitive to other factors.

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3 Responses to Genetic Risk Prediction: The Difference Between Diagnostics and Research

  1. Edward says:

    Limited forms of genetic risk prediction are already in use. For example, some women who carry a mutation in one of the BRCA genes are choosing to undergo preventative mastectomies. Also, it is possible to have quantitative measures of increased risk, so I’m not sure what your point is there? I agree that a test needs to be quantitative to be useful. Say the test result is: The population risk for this disease is 1 in 10,000, but based on your genotype, your risk is 1 in 100. How is that not useful? One can then hopefully take preventative measures or increase screening.
    I will agree than many of the genetic risk tests that are on the market are not ready for prime time, but a few are.

  2. Hi Mike,
    I completely agree with you that most personal genomic information (especially risk prediction for complex diseases using common, small-effect variants) isn’t ready for clinical practice. So I’m not arguing that genome scan profiles should be used by doctors, but simply that they should be available to consumers who want them, so long as all of the relevant caveats are spelled out during the purchasing process. (I’m not saying you misunderstand me here, I just wanted to make my position clear.)
    So where we disagree is on the matter of whether a predictive test of reasonably well-confirmed scientific validity but limited or no clinical utility should be available at all to consumers. Here I take a fairly libertarian stance: so long as the companies provide accurate material spelling out the caveats, I think the benefits of increasing genetic literacy amongst personal genomic customers will outweigh the harm done by people over-interpreting their results. In fact, I’ve argued in the past that the confusion engendered by personal genomic data is the best way for people to learn about the fuzzy, probabilistic nature of genetic predictions, and to counter the “gene for…” mentality in the popular media.

  3. @Daniel,
    “So long as the companies provide accurate material spelling out the caveats”
    Which are? We don’t even know if this is a real risk in your ethnicity? If they did that, no one would buy their tests……They have a disincentive to put it upfront, rather than in the “fine print”
    “I think the benefits of increasing genetic literacy amongst personal genomic customers will outweigh the harm done by people over-interpreting their results.”
    Ok, so let’s remove the health hacker mentality which applies to less than 1% of the population. The rest, which I have seen a few of, have no clue what this means and can’t figure it out on their own…..see my editorial in Nature Biotech….Mass confusion for why?
    “In fact, I’ve argued in the past that the confusion engendered by personal genomic data is the best way for people to learn about the fuzzy, probabilistic nature of genetic predictions, and to counter the “gene for…” mentality in the popular media.”
    If you can get someone to understand the nuances……
    That is a pretty big assumption Daniel.
    My take is this, let them be transparent and upfront. They (DTC GENOMICS COMPANIES) haven’t IMHO shown any desire to do that. Why would they? It would cause them to lose even more sales……
    -Steve

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