Alzheimer's disease experts are proposing new ways to diagnose the neurological condition, arguing that the existing criteria are out of date.

Alzheimer's is the most common form of dementia and is characterized by progressive memory loss, cognitive deterioration, and other behavioural changes.

The experts say that doctors are now better able to accurately diagnose the disease because of advances in structural MRI, molecular neuroimaging with PET, and cerebrospinal fluid analyses.

To meet the new criteria for probable Alzheimer's, the experts suggest that patients must show progressive memory loss over more than six months, plus at least one or more of the following biomarker criteria:

• atrophy in a particular part of the brain shown by MRI,
• abnormal biomarker proteins in the cerebrospinal fluid,
• a specific pattern on PET of the brain,
• and a genetic mutation for AD within the immediate family.

Currently, there is no definitive diagnostic biomarker for Alzheimer's and doctors can only make a "possible" or "probable" diagnosis based on evaluation of symptoms and through cognition tests.

The existing criteria were published in 1984 by the National Institute of Neurological Disorders and Stroke-Alzheimer Disease and Related Disorders (NINCDS-ADRDA) working group.

The authors say their proposed new criteria are an improvement over current methods.

"These new criteria are centred on a clinical core of early and significant episodic memory impairment," say the authors of the proposal, put forward in a Position Paper to be published in the August edition of The Lancet Neurology.

"The timeliness of these criteria is highlighted by the many drugs in development that are directed at changing pathogenesis."

"These proposed criteria... aim to define the clinical, biochemical, structural, and metabolic presence of AD."

In an accompanying comment, Dr Norman Foster, Center for Alzheimer's Care at the University of Utah, says: "We should seize this opportunity to reopen the discussion of Alzheimer's disease diagnosis. The time is right to use the advanced technology at our disposal to improve the early, accurate diagnosis of dementia and develop more effective treatments."