WASHINGTON (NEWSnet/AP) — New blood tests could help doctors diagnose Alzheimer’s disease more accurately, researchers said Sunday.

Labs have begun to offer tests that can detect signs of Alzheimer's in blood. The tests aren't used widely, because there's little data to guide doctors about which type to use. U.S. Food and Drug Administration hasn't given approval.

Alzheimer’s telltale “biomarkers” are amyloid plaque and abnormal tau protein that leads to neuron-killing tangles.

New drugs, Leqembi and Kisunla, can slow symptoms by removing amyloid from the brain. But they work only in early-stage Alzheimer's. Measuring amyloid in spinal fluid is invasive. A PET scan to spot plaque is costly.

Blood tests have been used mostly in controlled research settings. But a new study of about 1,200 patients in Sweden shows promise. Patients who visited either a primary care doctor or a specialist for memory complaints got initial diagnosis using traditional exams, gave blood for testing and were sent for a spinal tap or brain scan.

Blood testing was far more accurate, Lund University researchers said Sunday at Alzheimer's Association International Conference in Philadelphia. The doctors' initial diagnosis was 61% accurate and the specialists' 73%, but the blood test was 91% accurate, according to the findings, which were published in Journal of American Medical Association.

Dr. John Hsiao of National Institute on Aging said tests measure different biomarkers. Maria Carrillo, chief science officer at Alzheimer’s Association, said doctors and researchers should use blood tests proven to have at least 90% accuracy. The test most likely to meet that benchmark is p-tau217, Carrillo and Hsiao agreed.

Schindler helped to lead a comparison of several kinds of blood tests, funded by Foundation for the National Institutes of Health, that came to the same conclusion.

The test measures a form of tau that correlates with plaque buildup, Schindler said. A high level signals likelihood a person has Alzheimer’s. Low level indicates it probably is not the cause of memory loss.

Several companies are developing p-tau217 tests, including ALZpath Inc., Roche, Eli Lilly and C2N Diagnostics, which supplied the version used in the Sweden study.

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