MAPT and Alzheimer disease: The certainty was higher in participants with a pre-PET diagnosis of AD (from 7.6 [SD, 1.7] to 8.2 [SD, 2.0]; P < .001) and increased even further in participants with a tau PET positive result supporting an AD diagnosis (from 8.0 [SD, 1.4] to 9.0 [SD, 0.9]; P < .001).