Tag Archive for 'screening'

Identical twins usually do not die from the same thing

Over at Nature News, Erika Check Hayden has a post about a recent Science Translational Medicine paper by Bert Vogelstein and colleages looking at the potential predictive power of genetics. The take-home message from the study (or at least the message that has been taken home by, e.g., this NYT article) is that DNA does not perfectly determine which disease or diseases you may get in the future. This take home message is true, and to me relatively obvious (in the same way that smoking doesn’t perfectly determine lung cancer, or body weight and dietary health doesn’t perfectly determine diabetes status).

A lot of researchers have had a pretty negative reaction to this paper (see Erika’s storify of the twitter coverage). There are lots of legitimate criticism (see Erika’s post for details), but to be honest I suspect that a lot of this is a mixture of indignation and sour grapes that this paper, a not particularly original or particularly well done attempt to answer a question that many other people have answered before, got so much press (including a feature in the NYT). A very large number of people have tried to quantify the potential predictive power of genetics for a number of years – why was there no news feature for me and Jeff, or David Clayton, or Naomi Wray and Peter Visccher, or any of the other large number of stat-gen folks who have been doing exactly these studies for years. ANGER RISING and so forth.

But of course, the reason is relatively obvious. Continue reading ‘Identical twins usually do not die from the same thing’

A case study in personal genomics

I have no strong family history of any disease, despite having 7 blood aunts and uncles and countless cousins. So when I sent my spit off to 23andMe at the start of the Genomes Unzipped project, I was expecting something very similar to Caroline’s experience: a 5% increase in risk here, a 2% decrease in risk there, nothing that would really tell my anything about my health.

However, this was not my experience. Along with a pretty interesting Y haplogroup, I also had three unexpected and potentially worrying health results. I am a cystic fibrosis carrier, a hemochromatosis compound heterozygote, and have a strongly elevated risk of age-related macular degeneration. This cocktail of genetic disease certainly was not what I came to the test expecting!

After some thinking, I decided to take my test results to my GP, and see if there was any advice or testing he would recommend. In the end, my GP referred me to a clinical geneticist, which started a cascade of appointments which in turn led to a number of important changes in how I treat my own health.

What was most interesting is how the whole experience got me thinking about my health as something I am in charge of. I have since made a number of important life-style changes, some of them directly related to my genotyping results, some more generally to improve my overall health.

The point of this post is just to go through some of the experiences, what I have learned about specific conditions, and what changes I have made to my life since. In some sense, I feel like my experience is a case-study in what good outcomes can come from personal genomics, both for specific conditions, and more generally for how genetic data can change your own approach to your health.

Continue reading ‘A case study in personal genomics’

How well can a screening test predict disease risk?

We can usually be pretty confident that if our genotyping results say we carry a certain genetic variant, we really do carry that variant.  So why doesn’t that necessarily equate to a confident prediction about disease risk?  As Caroline outlined in her previous post on the risks and benefits of population screening, the results of screening tests (genetic or otherwise) may not provide a definitive diagnosis.  Test results often just categorise people as being at high or low risk of disease.  In this post, we’ll look at some of the ways we assess the predictive ability of a diagnostic test, and why the results we get from them are usually probabilistic.

Continue reading ‘How well can a screening test predict disease risk?’

Risks and benefits of population screening

The concept of screening is bandied around quite a bit these days, particularly associated with genetics and genome profiling for both common and rare diseases. But the term is often used without due consideration or understanding of the issues associated with screening itself. If we are to critically assess the potential for personal genomics to prevent disease in individuals and populations, we need to understand some underlying public health principles.

So what is screening? Most importantly, medical screening generally involves testing (apparently) healthy people, rather than individuals with a particular clinical problem. This simple statement comes with quite a bit of baggage – if you go around telling healthy people that they have (or are likely to develop) some hideously awful disease, and need some rather unpleasant treatments to stop it, you really want to be sure that you’re right! Which means being certain that the test used is strongly predictive of the disease in question, rather than just being mildly associated with it, and that it can be used to reliably discriminate between those who have or will get the disease and those who don’t and won’t.

Continue reading ‘Risks and benefits of population screening’

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