Alzheimer’s disease can be hard to definitively diagnose, but one study’s findings could make the process much easier and more accurate. Interim results from a 4-year analysis suggest that a substantial number of patients being treated for the condition may not have it at all, The Washington Post reports. The presence of amyloid plaque in the brain precedes Alzheimer’s and can be detected by costly positron emission tomography (PET) scans, which are not usually covered by insurance. Therefore, doctors often diagnose and treat patients for the disorder based on symptoms. After administering PET scans to 4000 people previously diagnosed with either mild cognitive impairment (MCI) or dementia and treated for Alzheimer’s to test for the presence of amyloid plaque, only 53.3% of patients with MCI and 70.5% with dementia tested positive. Following the results, doctors changed the care plans of two-thirds of the patients involved in the study, presenters said at the Alzheimer’s Association International Conference in London. Researchers hope the results will move the Centers for Medicare & Medicaid Services to cover PET scans through Medicare.