Alzheimer’s Disease is only one cause of dementia. Until recently the diagnosis was based on the clinical symptoms along brain images the brain showing atrophy. The diagnosis was confirmed with a brain biopsy. Now there is an assay of proteins in the cerebrospinal fluid (CSF) can help specify the diagnosis.

Despite more than 5 million Americans with Alzheimer's disease, and millions more at risk, these CSF tests have yet to be widely adopted by neurologists. In part because the ability to make an improved early diagnosis raised the question: does this matter? The argument in favor of earlier diagnosis is being able to treat the disease and thus slow the progression. However, not only is there no "magic bullet" for the prevention of Alzheimer's disease, there is no bullet at all. The current treatments offer modest, temporary, and symptomatic improvement at best.
A more persuasive argument in support of the CSF test is this provides more accurate diagnosis when testing new, possibly effective, treatments. The success of clinical trials requires not only that the treatment be effective, but that all subjects be correctly diagnosed. Subjects who have other diseases contaminate the sample and confound results.

At present, CSF and other biomarker Alzheimer's testing should be reserved for patients who present a diagnostic dilemma and patients entering clinical trials.