Still no cure, but the discovery of a simple advance warning test for Alzheimer's holds great promise

It will still take some years before this test can be developed into a commercial form

A simple test for Alzheimer’s disease that can accurately predict whether someone is going to develop this distressing condition could be seen as raising more problems than it is worth. Leaving aside its 90 per cent accuracy, which could lead to one in 10 people being given a “false positive” result, one may wonder what good could come from confirmation of a condition for which there is no cure.

Would anyone welcome being told that they are going to develop – and very likely die from – an incurable disorder that will eventually rob them of their memories, emotions and personality over a period of many years?

There is little doubt that Alzheimer’s disease, and dementia in general, is one of the most formidable health challenges facing Britain, and indeed the world, in the 21st century. Some 800,000 people in the United Kingdom already have some form of dementia, more than half of whom suffer from Alzheimer’s. With our increasing lifespans this figure is set to rise to more than a million within 10 years and by a further 1.7 million by mid-century. And all these people will need care for the rest of their lives – sometimes for several decades.

At present, it is only possible to diagnose Alzheimer’s and dementia when the symptoms become apparent, which is long after the machinery of the brain has already begun to malfunction at a biochemical level. However a simple blood test which provides an early warning two or three years in advance of its onset has now been achieved by scientists at Georgetown University in Washington. This is a considerable scientific breakthrough.

It will still take some years before this test can be developed into a commercial form that is properly validated for false negative and false positive accuracy. Even so, some medical ethicists may wonder what good such a test will do given that there is no current effective treatment for Alzheimer’s.

This is not the first time that medical science has been here. A blood test for HIV was available long before there was an effective treatment for Aids in the form of anti-retroviral drugs. As soon as it became obvious that Aids was not an inevitable death sentence, the HIV test was touted as a vital weapon against the disease because it identified those who needed therapy.

This blood test for Alzheimer’s therefore should not be seen simply as a way of signalling the thumbs-up or thumbs-down for a possible death sentence. It should be welcomed rather as a means of better understanding this complicated brain disease by giving scientists early warning of who is going to develop the condition.

One in three of us will suffer dementia at some time over the age of 65. Being able to identify, at an early stage, which of us will go down this path could rapidly accelerate the rate of scientific discovery, leading to more effective therapies, whether they are based on drugs or some kind of early cognitive intervention to delay the onset of the decline.

So we should not be afraid of this test for Alzheimer’s. We should welcome it.