Would you want to know if you had dementia many years before you developed symptoms?

Scientists have recently discovered that a blood test detecting specific proteins could predict dementia up to 15 years before a person receives a confirmed diagnosis. The researchers found 11 proteins that they say have a 90 per cent accuracy in predicting future dementia.

Researchers at the University of Warwick in England and Fudan University in China examined blood samples from 52,645 healthy volunteers from the UK Biobank genetic database between 2006 and 2010. Over the almost 15-year follow-up period, about 1,400 developed dementia.

The researchers used artificial intelligence and machine-learning to analyse 1,463 proteins in the blood. They identified 11 proteins associated with dementia, of which four could predict dementia up to 15 years before a clinical diagnosis.

Would you be in the queue to have this test done?

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I certainly would not and would be horrified if this test were to become commercially available and put into routine use.

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Making a definitive diagnosis of dementia can be difficult. It relies on various methods, including a lumbar puncture to look for certain proteins in the spinal fluid, PET (positron emission tomography) scans and memory tests. Many people remain undiagnosed until they develop memory and cognitive problems.

Digital technologies to aid the earlier detection of dementia are under development. These include traditional cognitive screening tools presented on mobile devices and passive data collection from wearable, in-home and in-car sensors. But these are light years away from having a random blood test, that although you feel well at the time of testing, places a Sword of Damocles over your future health.

It is worth assessing such a test against the principles of ethical screening programmes. Health screening is commonly undertaken to identify individuals who are deemed at higher risk for disease for further diagnostic testing. The purpose of the screening is that they can benefit from interventions that are proven to modify the natural course of the disease.

An acceptable screening programme must have the following features:

• The natural history of the disease should be understood.
• There should be a recognisable early symptomatic stage of the condition.
• There should be a test that is easy to perform and is acceptable to the population.
• The test used should be accurate.
• There should be an accepted treatment recognised for the disease.
• There should be an agreed policy on who to treat.
• Diagnosis and treatment should be cost-effective.
• Case-finding should be a continuous process and not just a “one-shot” test.

Using these criteria, it is clear that a predictive blood test for future dementia falls at a number of fences, including: there is currently no available treatment that improves the prognosis of someone diagnosed with dementia; progression from early-stage disease to dementia is neither certain nor currently predictable; the test is not highly accurate; the acceptability of early dementia detection is not established; and resources would be needed to ensure follow-up and support for those flagged by any new dementia screening system.

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The research, published in Nature Aging, does not address the ethical aspects of an early dementia diagnosis. However, a recent poll from the University of Michigan suggests we should be concerned. Researchers found that almost three-quarters of older adults said a positive result from an Alzheimer’s blood test would make them believe they were likely to develop Alzheimer’s disease; nearly two in three adults (64 per cent) said such a result would likely cause them significant distress. And nearly 80 per cent of those surveyed said they would consider changes to their financial or advance care planning if a blood test result came back positive.

So would you want to know if you or a loved one had dementia – a disease that currently has no treatments to stop or prevent it – many years before you developed symptoms?

While this is an interesting question for debate, from an ethical perspective I do not think it is a question we should ever be forced to ask or answer.

mhouston@irishtimes.com