ATMOSPHERE - Diagnosing Alzheimer’s disease — the most common form of dementia — can be tricky, because there is currently no single test that can accurately identify the condition. The only way to definitively know someone had Alzheimer’s while alive is by examining brain tissue after the person has died, according to the National Institute on Aging.
But as several presentations at the recent Alzheimer’s Association International Conference (AAIC) demonstrated, scientists may be getting closer to developing a blood test to screen people for Alzheimer’s disease and other forms of dementia. The AAIC conference took place July 14 to 18 in Los Angeles.
How Dementia and Alzheimer’s Are Diagnosed Today
Doctors currently can make a diagnosis of probable dementia by evaluating a person’s memory and thinking abilities through standardized questionnaires and by assessing anecdotal reports about their behavior. But other conditions, such as depression, brain tumors, nutritional deficiencies, and thyroid problems, can mimic symptoms of dementia and must be ruled out.
If a person has signs or symptoms of dementia, a doctor may order brain scans, such as MRI (magnetic resonance imaging), CT (computed tomography), or PET (positron emission tomography) to look for abnormalities that may help determine the underlying cause. Certain types of imaging can show how well the brain is using glucose and oxygen; reductions in oxygen and glucose reaching the brain have been related to Alzheimer’s.
The Potential of Biomarkers
Previous research suggests that accumulations of beta-amyloid protein may be a major contributor to the development of Alzheimer’s disease. Buildups of beta-amyloid disrupt communication between brain cells and eventually destroy them.
Evidence also indicates that a protein called tau may play a role in Alzheimer’s-related brain changes. Abnormal tau can collect inside neurons related to memory function.
Currently, both these biomarkers (short for biological markers) can be measured in spinal fluid, but the technique requires a spinal tap, which is invasive, and measurements can be inconsistent, according to the Alzheimer’s Association.
“Today, there is a global race to uncover better ways that we can understand the changes that might be happening to our brains and bodies as we are aging that are related to dementia or Alzheimer’s disease specifically,” says Rebecca Edelmayer, PhD, the director of scientific engagement at the Alzheimer’s Association.
“What we’re seeing right now is really a focus on looking at blood as a tool and developing reliable tests or indicators of how the blood can help determine what is happening in the brain,” she adds.
Amyloid Protein Blood Test May Detect Early Stages of Disease
At the AAIC, Akinori Nakamura, MD, PhD, a researcher at the National Center for Geriatrics and Gerontology in Obu, Japan, highlighted results from an innovative test that measures abnormal versions of amyloid protein in the blood.
Dr. Nakamura and his colleagues analyzed blood samples from 201 individuals who either had probable Alzheimer’s, another form of dementia, mild cognitive impairment, or no symptoms based on brain scans and behavioral tests.
The amyloid blood exam correctly identified 92 percent of the individuals thought to have Alzheimer’s. Study authors calculated that the test had an 88 percent accuracy rate.
“This study is really focused on correlating the amount of amyloid beta in the blood to some of the amyloid beta that can be seen through amyloid PET imaging in the brain, as well as cognitive scores,” says Edelmayer.
Nakamura notes that this plasma biomarker may detect earlier stages of amyloid deposition, even before dementia symptoms are apparent.
“Our results suggest that the plasma biomarker may be useful in screening people who are at risk for Alzheimer’s,” he said in a statement. “This can facilitate clinical trials for Alzheimer’s therapies and also accelerate studies to investigate the effects of nondrug interventions, risk management, and lifestyles on Alzheimer’s progression.”[EDH]