Blood test accurately diagnosed Alzheimer’s 90% of the time, study finds

The results are the latest milestone in the search for affordable and accessible ways to diagnose the disease.

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% 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% of the time, while primary care doctors using those methods got it right only 61% of the time.

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 7 million Americans and more than 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.

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

The new research was conducted in Sweden, and experts cautioned that, for use in the United States, the results should be confirmed in a diverse American population.

Experts emphasized that blood tests should be only one step in a screening process and, most importantly, should be used only for people with memory loss and other symptoms of cognitive decline — not for people who are cognitively healthy to predict if they will develop Alzheimer’s.

Testing recommendations could change if scientists find drugs that can delay or halt Alzheimer’s pathology in people who have not yet developed cognitive problems.

Medical experts also said that blood tests should be performed only after administering tests that assess memory and thinking abilities and CT scans that seek alternative causes like strokes or brain tumors. And blood test results should be confirmed by one of the gold-standard methods: PET scans or spinal taps to measure a protein, amyloid, that accumulates and forms plaques in the brains of patients with Alzheimer’s.