The findings, presented Wednesday at the Alzheimer’s Association International Conference in London, come from a four-year study launched in 2016 that is testing over 18,000 Medicare beneficiaries with mild cognitive impairment (MCI) or dementia to see if their brains contain the amyloid plaques that are one of the two hallmarks of the disease. Among 4,000 people tested so far in the Imaging Dementia-Evidence for Amyloid Scanning (IDEAS) study, researchers from the Memory and Aging Center at the University of California at San Francisco found that just 54.3 percent of MCI patients and 70.5 percent of dementia patients had the plaques. Amyloid plaques start developing 15 to 20 years before the symptoms of Alzheimer’s disease start to show, and testing positive wouldn’t mean that a person is definitely going to develop the condition. (National Institute of Biomedical Imaging and Bioengineering) 
 
 “If someone had a putative diagnosis of Alzheimer’s disease, they might be on an Alzheimer’s drug like Aricept or Namenda,” said James Hendrix, the Alzheimer Association’s director of global science initiatives who co-presented the findings.  In this photo taken July 12, 2017, Cynthia Guzman plays dominoes at her home in Napa, Calif. Guzman underwent a special kind of PET scan that can detect a hallmark of Alzheimer’s and learned she didn’t... (Associated Press) 
 
 WASHINGTON (AP) — Does it really take an expensive brain scan to diagnose Alzheimer's? "To get that right diagnosis, that's really important," said Cynthia Guzman of Napa, California, whose initial Alzheimer's diagnosis was ruled out in an earlier PET scan study. Deyan Georgiev / EyeEm / Getty 
 
 A blood test can detect whether plaques of beta-amyloid are building up in a person’s brain – a sign that they may develop Alzheimer’s disease. Until now, the only way to monitor plaque build-up in a person’s brain has been through expensive PET-scans, or by performing an invasive spinal tap procedure. Over 400 physicians enrolled their patients in the study, and they initially filled out forms describing how they would care for them based on their clinical symptoms. Researchers check if doctors' initially recorded treatment plans — medications, counseling or additional testing — were altered by patients' PET results.
– Diagnosing Alzheimer's is a guessing game—and many doctors are guessing wrong, according to early results from a new study presented Wednesday in London. The Washington Post reports doctors tested 4,000 Medicare patients with mild cognitive impairment or dementia and discovered many of them definitively do not have Alzheimer's. Using PET scans, the study revealed only 54.3% of mild cognitive impairment patients and 70.5% of dementia patients had brains containing amyloid plaques. These plaques can be a sign of Alzheimer's. The patients who had them may or may not have Alzheimer's; the remaining percentage definitely don't have the disease. "To get that right diagnosis, that's really important," one woman, whose Alzheimer's diagnosis was ruled out by a PET scan, tells the AP. The findings show many people are potentially taking unnecessary Alzheimer's medication, and doctors may want to change their treatment to something cheaper or more effective. Unfortunately, the only ways to test for amyloid plaques while a patient is alive are expensive PET scans, which aren't usually covered by insurance, or invasive spinal taps. Or are they? Another study presented at the same London conference revealed a new blood test that could potentially reveal the plaques, New Scientist reports. The tests are easy and cheap enough that doctors could administer them to patients during regular checkups. Since plaques start showing up 15 to 20 years before Alzheimer's symptoms, patients could use the results to change certain lifestyle habits to decrease their risk. (This startup buys young blood, injects it into older people.)