Alzheimer’s is diagnosed by tests and some elimination of other diseases. When doing a dementia diagnosis, generally the doctor starts with a physical exam to rule out medication issues and other medical problems that can be fixed. Then they often go to psychological exams, such as the Mini Mental State exam. Also, many doctors order a PET scan of the brain.
Every good exam should have many questions about the individual, such as what they did for a living and what they are good at and not so good at, so that the doctor can look for changes. Change in abilities is a big factor how Alzheimer’s is diagnosed.