Though increasingly common, Alzheimer's disease still isn't all that easy to diagnose, especially in its early stages.
Forgetfulness and other signs of dementia can be caused by lots of things other than Alzheimer's. Sometimes the symptoms are fleeting or normal in the context of a person's age. But at other times these symptoms mark the dark path of Alzheimer's.
Doctors' standard approach to diagnosis includes taking a medical history of the patient, assessing mental function and administering various neurological and lab tests.