Blood test accurately diagnoses 90% of Alzheimer’s cases

The path to better diagnosis and faster access to clinical trials and early treatment for Alzheimer’s disease includes blood tests, according to research that was presented at the Alzheimer’s Association’s International Conference in Philadelphia this week.

Findings were also published in the Journal of the American Medical Association.

In the research, a blood test is about 90% accurate in identifying Alzheimer’s disease, the most common form of dementia, in people who have cognitive symptoms and visited a specialized clinic or primary care doctor. In contrast, the primary care physicians were about 63% accurate and the specialists were 73% accurate in making the diagnosis without a blood test.

“Highly accurate” blood tests are “moving closer to use in physician’s offices,” the Alzheimer’s Association said in a news release .

Current diagnosis typically depends on a series of tests and what are well-educated assessments by physicians. Positron emission tomography, or PET, scans and spinal taps to look at cerebrospinal fluid, which are expensive and sometimes hard to access, are used to verify Alzheimer’s.

The disease is marked by a buildup of amyloid beta plaques and tau tangles in the brain.

“Blood tests that show the most promise for identifying Alzheimer’s-related changes in the brain assess phosphorylated tau (p-tau) protein, an Alzheimer’s biomarker that can build up before patients show signs of cognitive impairment,” the association wrote. “Increases in the specific marker p-tau217 over time correlate with worsening cognition and brain atrophy. The p-tau217 test also predicts the likelihood of amyloid plaques in the brain, which are another biomarker for Alzheimer’s and the target for recently approved treatments.”

The association has gathered a panel of experts on Alzheimer’s disease to come up with clinical practice guidelines on how blood biomarkers should be used to diagnose the disease, which directly impacts nearly 7 million people in the United States, with the numbers growing as the population ages.

For the study, 1,213 patients were tested with the PrecivityAD2 test, administered in either a doctor’s office or a specialty clinic. The test was highly accurate even when the patient had other health issues like kidney disease. That’s important because most of the people with Alzheimer’s are older adults and that’s a population that frequently has other health issues, as well.

Senior study author Dr. Oskar Hansson, of Lund University in Sweden, called the research a “major step towards global clinical implementation of an Alzheimer’s blood test. “It highlights the need for Alzheimer’s biomarkers in making a correct diagnosis more of the time.”

Among next steps, he said, is establishing those “clear guidelines” on how an Alzheimer’s blood test should be used by clinicians to diagnose the disease.

A sense of urgency

After years of waiting and longing on the part of advocates, patients and family members, there are now several medications approved to treat Alzheimer’s disease, though none of them provide a cure. Instead, they slow progression somewhat.

But the new drugs are all approved for early-stage disease, which makes it urgent for people to get diagnosed and seek treatment early. And proper diagnosis is also crucial to participate in clinical research, which is often the best way to access new treatment options.

The study looked at wait times to access treatment, using proven forecasting models that took into account both the limited number of Alzheimer’s disease specialists and the growing older population. The projections centered around the growing population of people who would be at least 55 between 2023 and 2032.

Researchers tried two scenarios: Primary care doctors could decide, based on a brief cognitive test, whether to refer someone to a specialist. Or that primary care doctor could look at results of a “high performance blood test” and that would factor into referrals.

Right now, it’s taking so long to get people in to see specialists that by the time they get there, it’s too late to try some of the most promising new medications, said Dr. Soeren Mattke, lead author of the study and director of the Brain Health Observatory at the University of Southern California.

A diagnostic blood test could make a big difference in that, he noted.

In the research model, by 2033 people would wait about six years to see if they qualified for new treatments, based on the brief cognitive testing method. But a blood test could rule out Alzheimer’s and drop a bunch of people who are trying to see specialists from needing one, reducing the average wait to 13 months. And it gets better, the researchers said. If a primary care doctor could use the blood test and the brief cognitive test to rule out Alzheimer’s, wait times for those with the disease who are seeking treatment could drop to an average of less than six months.

Blood tests often used to diagnose

A number of companies are developing blood tests to find biomarkers of Alzheimer’s and other diseases.

In November, Provo-based Resonant, a subsidiary of Renew Biotechnologies, reported its research on a novel blood biomarker of neurodegeneration.

Its study, published in Frontiers in Neuroscience , said the technology “achieved a remarkable 100% accuracy in identifying patients with Alzheimer’s disease and individuals with mild cognitive impairment, the clinical precursor, that developed Alzheimer’s disease within five years.”

Resonant looks for type-specific neuron death biomarkers. It employs the same concept with other neurodegenerative diseases, including Parkinson’s and amyotrophic lateral sclerosis.

Blood tests are also a diagnostic helper for diabetes and some forms of cancer, including leukemia and lymphoma. It’s not diagnostic, however, for solid-organ tumors like lung, breast or colon cancer, according to the Cleveland Clinic .

Even when they aren’t diagnostic, the Mayo Clinic says blood tests can offer clues about diseases like cancer, such as how well your organs are functioning and whether you have various proteins or other substances that are made by cancer. If the blood test results indicate cancer is possible, a biopsy or other tests are often used to make the diagnosis.