Doctors expressed optimism at the progress researchers have made with a new blood test aimed at detecting Alzheimer’s disease at an early stage. 

They told FOX Business that they have waited years for a more accessible and affordable way to detect the diease, and now, it is one step closer to becoming a reality. 

The latest development of the test, published in JAMA Neurology on Monday, revealed a protein called phosphorylated tau 217 assay could be used to detect the disease up to two decades prior to the onset of symptoms. 

Test researchers discovered that p-tau217 assay has greater than 90% accuracy for diagnosing Alzheimer’s disease, Dr. Sharon Cohen, a behavioral neurologist, told FOX Business. 

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The data underscored how the blood test can track disease progression without forcing patients to go through the expensive positron emission tomography (PET) scans and invasive procedures such as spinal fluid assessments, according to Cohen and New York City-based emergency room physician Dr. Robert Glatter.

It has been a long time coming. 

"We have wanted a blood test for Alzheimer's for years, and initially that just seemed impossible," Cohen said. However, given that "the need is so great to have an accessible, affordable way of diagnosing Alzheimer's disease early in the disease when treatments might be helpful, scientists around the world have continued to work on this." 

A test like this can make an early and accurate diagnosis more readily available.

Cohen and Glatter believe it can be a game-changer for Alzheimer's disease, which is the most common type of dementia, because it can lead to improved patient care and treatment options. 

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According to latest estimates from the Centers for Disease Control and Prevention, about 6.7 million Americans who are at least 65 years old are living with Alzheimer's in 2023. However, that figure is expected to nearly triple to 14 million people by 2060.

"Having such a blood test with high accuracy will be a game change in the management of patients at higher risk for Alzheimer’s Disease, especially those who have a strong family history," Glatter said. 

Cohen said the word "game-changer" gets tossed around a lot, but she agreed that in this case, it fits. 

"If we can have a blood test that we can use in clinical work in a doctor's office, not just in the research setting, that will really allow us to move forward with Alzheimer's disease diagnosis" and early treatment, she continued. 

The disease is very long and creeps up gradually before people are cognitively impaired.

The issue is that even if people have subtle symptoms, "we just brush them off because everybody complains of being a little bit absentminded or forgetful as they get older, and we don't think of people who are disabled by forgetfulness as having Alzheimer's," she continued. 

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It explains why Alzheimer's is often undiagnosed. In other cases, patients do not want to undergo an invasive procedure, or they do not have the finances to undergo PET scans which cost thousands of dollars, Cohen said. Even if they do, some patients, especially in rural settings, may have to travel far to even get access to them.

In some cases, patients avoid them because they are worried about the outcome.

"A lot of people have been fearful about, you know, 'why would I want to find out that I have Alzheimer's if there's nothing you can do?'," Cohen noted.

She is trying to change this perception. Not only are there things that they can do, but they can help people "even more effectively if we catch the diease early." 

Cohen said, "it's a very hopeful time" for Alzheimer's disease with better diagnostics and treatments coming to the market that slow the disease.

Over the summer, the FDA even approved an Alzheimer's drug, Leqembi, which Cohen previously told FOX Business is the first drug that has been shown to "slow down the clinical aspects of Alzheimer's disease, meaning people will lose memory at a slower rate and lose their functional abilities at a slower rate." 

With such developments, Cohen believes people will feel more hopeful about getting a diagnosis and acting on early findings rather than waiting." 

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The other good news is that this blood test could also help rule out the disease too. If the test is negative for p-tau217, for instance, then doctors can assess patients for other causes of neurological impairment such as vascular dementia or Lewy body dementia, according to Glatter.