A blood test that can predict whether a healthy person will develop Alzheimer's disease within three years has been discovered by US scientists.

The test is more than 90% accurate and it can also predict if a person will develop mild cognitive impairment, which can be a warning sign for dementia, including Alzheimer's.

The test focuses on 10 lipids (blood fats) and the scientists believe it could be ready for clinical use in as little as two year's time. This marks the first known published report on blood-based biomarkers in the period before Alzheimer's develops.

"Our novel blood test offers the potential to identify people at risk for progressive cognitive decline and can change how patients, their families and treating physicians plan for and manage the disorder," said Prof Howard Federoff of Georgetown University Medical Center.

Alzheimer's disease affects over 35 million people worldwide and some 35,000 people in Ireland. There is currently no cure or effective treatment for the condition.

According to Prof Federoff, a lot of studies have focused on slowing down or reversing the progression of the disease, however none of these have worked.

He believes this may be because such treatments were evaluated too late into the disease's progression. He said that the ‘pre-clinical state of the disease offers a window of opportunity for timely disease-modifying intervention'.

"Biomarkers such as ours that define this asymptomatic period are critical for successful development and application of these therapeutics," Prof Federoff noted.

The scientists' research included 525 healthy people aged 70 and older. All provided blood samples at the beginning of the study and at different periods throughout a five-year period.

During this time, 74 people met the criteria for mild Alzheimer's or a condition known as amnestic mild cognitive impairment (aMCI). Loss of memory is a major element of aMCI.

Further tests and analyses led to the discovery of a panel of 10 lipids which appeared to play a crucial role in those affected by the conditions.

"The lipid panel was able to distinguish with 90% accuracy these two distinct groups - cognitively normal participants who would progress to mild cognitive impairment or Alzheimer's disease within two to three years, and those who would remain normal in the near future," Dr Federoff said.

He insisted that these findings are a ‘major step towards the commercialisation of a pre-clinical disease biomarker test'.

This test could in the future be used for ‘large-scale screening to identify at-risk individuals', he added.

Details of these findings are published in the journal, Nature Medicine.

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