In addition to Jeff's excellent reply ... Current methods for "diagnosing" Alzheimer's are very laborious, involve all sorts of expensive testing, and in the end, the best we can do is say "probable" Alzheimer's.  The disease cannot be positively diagnosed unless and until a brain biopsy is done at autopsy.  There are dozens upon dozens of disorders that can cause dementia symptoms, most of which can be treated and many of which can be cured.  It is extremely important to develop reliable, inexpensive methods for ruling out Alzheimer's as well as diagnosing it.  And while there is no cure for Alzheimer's, there are medicines and medical foods that can help delay the progression of symptoms so that you and/or your loved one can enjoy a better quality of life for a longer time.