“Simple” blood test to predict if you’ll be alive in 5 years? Please….

The obsession that some in journalism have with “simple” blood tests – the unquestioning “test for everything” mentality that shines through in so many stories – is, itself, bloodcurdling.

Yesterday we wrote about how CNN stated that an Alzheimer’s test had “astonishing accuracy” – when another solid news story reported that “the accuracy fell short of what would normally be acceptable for a screening test.” CNN wasn’t alone in hyping that study, but so far at least, they lead the journalism world on this next one.

Today CNN.com reports on an observational study that made an association between four biomarkers and risk of death and reported:

Will you be alive five years from now? New research suggests it might be possible to predict if you’ll die from a medical condition in the next half-decade.

How, you ask? With a simple blood test.

According to a recent study published in the journal PLOS Medicine, if your blood registers high levels of four “biomarkers,” biological molecules found in your blood, body fluids, or tissues, you are at a substantially higher risk of dying in the next five years.

And that same CNN.com story appears on many TV station websites across the country.  Follow the leader.

But the leader is woefully incomplete on this one.

You don’t need to look any further than the “What Do These Findings Mean?” section of the published study.  It would seem that if you’re not quite sure about what the findings mean, you might want to at least refer to that section, which states (my emphasis added):

However, there are several limitations to this study. As an observational study, it provides evidence of only a correlation between a biomarker score and ill health. It does not identify any underlying causes. Other factors… might be the true cause of serious health problems and would provide a more accurate assessment of risk. Nor does this study identify what kinds of treatment might prove successful in reducing the risks. Therefore, more research is needed to determine whether testing for these biomarkers would provide any clinical benefit.

The observational nature of the study was not mentioned by CNN. An observational study can not establish cause-and-effect.  So talking about “risk” – as in CNN’s 5th sentence, “…you are at a substantially higher risk of dying in the next five years.” – is technically inaccurate.   Establishing risk means you’ve established cause-and-effect to define the risk. Anything else is fear-mongering about boogeymen at this point.

The CNN story’s final sentence – if you made it that far – read, “So don’t obsess too much over your annual blood tests just yet; more research is needed.” But that’s a far cry from the first five sentences of the story, which I posted above.  Stories like this – and yesterday’s Alzheimer’s test story – fuel the obsession that you now tell people to ignore in your final throwaway line.

My summary:

  1. If you ever hear anyone refer to a “simple blood test,” run away as fast as you can.  There is no such thing.
  2. Read the study.  When you see a heading such as “What Do These Findings Mean?” you may want to pay special attention especially if you’re not sure what it means.
  3. Do pay attention to CNN’s last line about not obsessing about your annual blood tests.  The problem is:  that should have been the headline for this and many other stories by CNN and others.


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