A Blood Test Accurately Diagnosed Alzheimer’s 90% of the Time, Study Finds

Scientists have made another major stride toward the long-sought goal of diagnosing Alzheimer’s disease with a simple blood test. On Sunday, a team of researchers reported that a blood test was significantly more accurate than doctors’ interpretation of cognitive tests and CT scans in signaling the condition.

The study, published Sunday in the journal JAMA, found that about 90 percent of the time the blood test correctly identified whether patients with memory problems had Alzheimer’s. Dementia specialists using standard methods that did not include expensive PET scans or invasive spinal taps were accurate 73 percent of the time, while primary care doctors using those methods got it right only 61 percent of the time.

“Not too long ago measuring pathology in the brain of a living human was considered just impossible,” said Dr. Jason Karlawish, a co-director of the Penn Memory Center at the University of Pennsylvania who was not involved in the research. “This study adds to the revolution that has occurred in our ability to measure what’s going on in the brain of living humans.”

The results, presented Sunday at the Alzheimer’s Association International Conference in Philadelphia, are the latest milestone in the search for affordable and accessible ways to diagnose Alzheimer’s, a disease that afflicts nearly seven million Americans and over 32 million people worldwide. Medical experts say the findings bring the field closer to a day when people might receive routine blood tests for cognitive impairment as part of primary care checkups, similar to the way they receive cholesterol tests.

“Now, we screen people with mammograms and PSA or prostate exams and other things to look for very early signs of cancer,” said Dr. Adam Boxer, a neurologist at the University of California, San Francisco, who was not involved in the study. “And I think we’re going to be doing the same thing for Alzheimer’s disease and hopefully other forms of neurodegeneration.”

In recent years, several blood tests have been developed for Alzheimer’s. They are currently used mostly to screen participants in clinical trials and by some specialists like Dr. Boxer to help pinpoint if a patient’s dementia is caused by Alzheimer’s or another condition.