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Sharon Roszel, 61, whose father died of Alzheimer’s a decade ago and whose mother is still struggling with the disease, says she would seize the chance for an early diagnosis.Glenn Lowson/The Globe and Mail

Researchers have developed a new blood test that may be able to tell individuals if they will develop Alzheimer's disease, years before any symptoms appear.

But with no cure for Alzheimer's, and with medication of only limited effect, such a predictive test poses a profound question for patients: Is it better to be aware of the approach of an inevitable disease, or to live on in relatively happy ignorance?

The new blood test for Alzheimer's, which used lipid levels in the blood to predict disease, was accurate 90 per cent of the time, according to a study published this week in Nature Medicine. Some of the patients involved were given an inaccurate or false positive result. Even if patients receive an accurate result, the test could present a slew of complications, from not being able to get life insurance to being unfairly dismissed from a job – or the simple worry of knowing that a debilitating disease awaits, years down the road.

Sharon Roszel, 61, whose father died of Alzheimer's a decade ago and whose mother is still struggling with the disease, says she would seize the chance for an early diagnosis. "I want to know," said Ms. Roszel, who lives in Hamilton. "So I can get things ready for myself and plus, do things now instead of wait."

Predictive tests that use biomarkers to assess a person's risk for a particular disease are becoming increasingly common as science evolves. Mimi Lowi-Young, CEO of the Alzheimer Society of Canada, says the ramifications can be far-reaching.

"You need to understand what the impact is around personal decisions, relationships with family, what impact it will have on family, children, finances and so on," she said. "Do people want to know about the chances of developing the disease when there's currently no cure?"

Many other so-called predictive tests, such as the prostate-specific antigen test, have come under fire in recent years as a result of research showing that it may lead to false positives and unnecessary treatment.

"I would want this to be as scientifically sound as possible before we move forward," said Timothy Caulfield, Canada Research Chair in Health Law and Policy at the University of Alberta.

If the results can be confirmed in larger trials that include a broader cross-section of the population, the blood test could radically change how the disease is diagnosed. It could give patients the chance to have much earlier access to medications that could stave off significant cognitive decline for extended periods.

It's a big if.

"[There's] a variety of things that need to be done to see if this holds up," said Barry Greenberg, director of neuroscience, drug discovery and development at the University Health Network and director of strategy at the Toronto Dementia Research Alliance, who was not involved with the study. "I'm afraid there's going to be a lot of enthusiasm and another potential for disappointment," Dr. Greenberg said.

Mark Mapstone, study author and associate professor of neurology at the University of Rochester Medical Center, said the results could represent an important development for a disease that is often difficult to diagnose and even more challenging to treat.

In the study, researchers followed a group of 525 seniors from Rochester, N.Y. and Irvine, Calif., and discovered that when the levels of 10 specific lipids in blood plasma were lower than normal, patients were more than 90 per cent likely to develop Alzheimer's or mild cognitive impairment (MCI).

Throughout the five-year study, 74 participants met the criteria for Alzheimer's or MCI and most of them had lower levels of 10 specific lipids in their blood before diagnosis. Dr. Mapstone said the lower lipid levels could correspond with a neurodegeneration that occurs before the symptoms of cognitive decline appear in patients.

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