What if you could find out, with a relatively high degree of certainty, whether you would get Alzheimer’s disease in the next few years? Would you want that information? Would the fact there is currently no cure or preventative treatment have an impact on your decision?
These are some of the questions raised by a recent study that suggests a seemingly straightforward blood test might be able to predict, with 90 per cent accuracy, the onset of Alzheimer’s. Over the past few days, news outlets throughout the world have hailed this research as a “breakthrough” that could lead to treatments that, as one article stated, could “halt or even prevent the disease.”
This is, no doubt, a potentially exciting development. The test, which measures the level of a variety of lipids in the blood, may help inform both research strategies and, one can hope, future therapies.
Still, we need to be cautious and resist the “breakthrough” mentality so pervasive in popular culture today. This is one study. And it is not a terribly large one. Nor is the predictive power as precise as often reported in the media (for example, the 90 per cent prediction refers to the onset of both mild cognitive impairment and Alzheimer’s disease – two very different outcomes). The results of the study are promising, but we need to take great care not to over-interpret or overreact.
History tells us that biomarkers are often not as prognostic as suggested by early research results. Indeed, a 2012 paper by Stanford University’s John Ioannidis concluded that, despite the large investment in biomarker research – such as genetics testing, body and tissue imaging and the measurement of particular chemicals in the blood – “the yield of successful biomarkers with unquestionably favorable health impacts has been extremely limited to date.” Other work by Mr. Ioannidis has found that the predictive power of biomarkers is often exaggerated in the scientific literature, thus making it difficult for clinicians to judge their true value.
So, when faced with the prospect of an exciting new test, such as this one for Alzheimer’s disease, we should remind ourselves to wait for the results of methodologically rigorous studies that replicate the initial findings.
Moreover, a consideration of the social and individual impact of the test needs to be weighed and investigated.
First, it is unclear that the likely onset of Alzheimer’s is something that all individuals would want to know, particularly since there is nothing that can be done to prevent or cure this fatal condition. While there is survey research that suggests a strong interest in this kind of technology (perhaps people will want to get things done prior to arrival of symptoms), experience with other predictive tests gives us some hint as to how the uptake might actually play out. A genetic test for Huntington’s disease, for example, has been around for decades. If an individual tests positive for the relevant genetic mutation, the future development of the disease is a virtual certainty. In other words, the test is 100 per cent predictive.
But despite the power of the test, only 10 to 20 per cent of individuals at risk for Huntington’s – that is, individuals with a family history – actually get tested. The majority of individuals simply don’t want to know what the future holds.
Second, there are questions about how individuals and our health system might react to this information. Would a positive result cause anxiety and, perhaps, enduring psychological harm? Research tells us that humans are, in fact, remarkably resilient to even the most distressing news. But it seems certain that at least some individuals would struggle with the prospect of imminent cognitive decline – a fact that seems particularly salient given that there would likely be a significant number of false positives.
And what impact might a test of this nature have on our health care system? Even inexpensive tests can have significant downstream costs.
Alzheimer’s disease is devastating. It is understandable that news of a noteworthy advance would result in hopeful headlines and predictions of near future application. Indeed, I too am hopeful that research of this nature will lead to effective tests, preventive strategies and, even, treatments.
But the announcement of and reaction to this study also highlights the need for caution in the interpretation of results, carefully executed replication studies and a consideration of the cascade of individual and social costs so often associated with potentially powerful medical advances.
There is a lot at stake. Let’s get it right.
Timothy Caulfield holds the Canada Research Chair in Health Law and Policy at the University of Alberta, is a Trudeau Fellow and is the author of The Cure for Everything: Untangling the Twisted Messages about Health, Fitness and Happiness (2012).
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