Blood tests for Alzheimer's may be coming to your doctor's office. Here's what to know

New blood tests could help doctors diagnose Alzheimer's disease faster and more accurately, researchers reported Sunday but some appear to work far better than others.

It's tricky to tell if memory problems are caused by Alzheimer's. That requires confirming one of the disease's hallmark signs a buildup of a sticky protein called beta-amyloid hard-to-get brain scan or uncomfortable spinal tap. Many patients instead are diagnosed based symptoms and cognitive exams.

Labs have begun offering a variety of tests that can detect certain signs of Alzheimer's in blood. Scientists are excited by their potential, but the tests aren't widely used yet because there's little data to guide doctors about which kind to order and when.

The U.S. Food and Drug Administration hasn't formally approved any of them, and there's little insurance coverage.

"What tests can we trust?" asked Dr. Suzanne Schindler, a neurologist at Washington University in St. Louis who's part of a research project examining that. While some are very accurate, "other tests are not much better than a flip of a coin." Demand for earlier Alzheimer's diagnosis is increasing More than 6 million people in the United States and millions more around the world have Alzheimer's, the most common form of dementia. Its telltale "biomarkers" are brain-clogging amyloid plaques and abnormal tau protein that leads to neuron-killing tangles.

New drugs, Leqembi and Kisunla, can modestly slow worsening symptoms by removing gunky amyloid from the brain. But they only work in the earliest stages of Alzheimer's, and proving patients qualify in time can be difficult. Measuring amyloid in spinal fluid is invasive. A special PET scan to spot plaques is costly, and getting an appointment can take months.