Therefore, neuropsychological testing does not "diagnose" Alzheimer's disease. A diagnosis of Alzheimer's disease relies on all of the information about the patient that is related to their thinking and memory. The testing may be part of this information, but it should not be the only source of the information being used to make a diagnosis of Alzheimer's disease. In this way, Neuropsychological Testing is the same as any other testing, including blood testing and brain scan testing (such as MRIs and CAT scans). It is a tool to be used by the doctor to assist him or her in making the diagnosis about the presence or absence of Alzheimer's disease.