Researchers in the United States say they have developed a blood test that can predict with more than 90 per cent accuracy whether someone will develop Alzheimer’s disease within three years.

Dr. Howard J. Federoff, professor of neurology at Georgetown University Medical Center, led a team that set out to find a set of molecules in healthy subjects that could predict whether they would develop either mild cognitive impairment or Alzheimer’s.

“That is exactly what we found,” Federoff said in a video statement issued by Georgetown on Sunday. The blood test identifies ten lipids, or fats, that predict disease onset.

For their study, the researchers enrolled 525 healthy subjects aged 70 and older who gave blood at the outset and at regular intervals. Over five years, 74 subjects met the criteria for either mild Alzheimer’s disease or amnestic mild cognitive impairment (aMCI), the main symptom of which is memory loss.

Comparing 53 of these subjects against the same number of cognitively normal subjects, the researchers discovered the ten lipids that they say revealed the breakdown of neural cell membranes in those that developed symptoms of cognitive impairment.

The discovery of the lipids was confirmed in the remaining subjects who developed either Alzheimer’s or aMCI against the same number of controls.

“The lipid panel was able to distinguish with 90 per cent accuracy these two distinct groups: cognitively normal participants who would progress to MCI or AD within two to three years, and those who would remain normal in the near future,” Federoff said.

The researchers say their study is the first that identifies blood-based biomarkers that predict Alzheimer’s. However, the test may not be ready for use in clinical studies for another two years.

Identifying patients who are most likely to develop Alzheimer’s could help scientists develop prevention and treatment methods that will delay, or perhaps even prevent, disease development. The team is designing a clinical trial to identify high-risk subjects in order to test just such a drug.

The findings are published in the April edition of the journal Nature Medicine.

Lisa Loiselle, an Alzheimer’s researcher at the University of Waterloo, says that if the test proves 100-per-cent accurate, it “could be very, very valuable.”

However, she told CTV News Channel Monday that she has some reservations about the study, including that the subjects were all 70 or older.

“Individuals who are 70 years of age and older generally have higher risk factors for developing dementia to begin with,” Loiselle said. “Those who are older also have a higher lipid count in their blood. So we have to take that into perspective.”

Loiselle said she would like to see the study’s results replicated in patients under age 70.

In his video statement, Federoff notes that more than 35 million people suffer from Alzheimer’s around the world, and by the middle of this century that figure is expected to balloon to more than 100 million.

Up to now, drugs that have been developed to slow the onset of disease have largely failed, but that could be because they were tested in patients who were already diagnosed; in other words, too late.

“The preclinical state of the disease offers a window of opportunity for timely disease-modifying intervention,” Federoff said. “Biomarkers such as ours that define this asymptomatic period are critical for successful development and application of these therapeutics.”