New diagnostic criteria for Alzheimer's disease

July 08, 2007

An international group of Alzheimer's disease (AD) experts have proposed new criteria for the reasearch diagnosis of the condition, as they argue the existing criteria are out of date due to unprecedented growth of scientific knowledge in the field. The proposal is put forward in a Position Paper published early Online and in the August edition of The Lancet Neurology.

AD is a neurodegenerative disease characterised by progressive cognitive deterioration, together with declining activities of daily living and by neuropsychiatric symptoms or behavioural changes. It is the most common form of dementia.

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.

Dr Bruno Dubois, Salpêtrière Hosptial, Paris, France, and colleagues, say: "[These existing criteria] are the prevailing diagnostic standards in research; however they have now fallen behind the unprecedented growth of scientific knowledge. Distinctive and reliable biomarkers of AD are now available through structural MRI, molecular neuroimaging with PET*, and cerebrospinal fluid analyses."

To meet the new criteria for probable AD, patients must show progressive memory loss over more than six months, plus at least one or more of the supportive biomarker criteria. These include: 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. The authors say: "These new criteria are centred on a clinical core of early and significant episodic memory impairment...the timeliness of these criteria is highlighted by the many drugs in development that are directed at changing pathogenesis."

The researchers add that validation studies are required to advance the new criteria and optimise their sensitivity, specificity and accuracy. They conclude: "When effective disease-modifying medications are available, the argument for such biologically based studies will be even more compelling.

"These proposed criteria move away from the traditional two-step approach of first identifying dementia according to degree of functional disability, and then specifying its cause. Rather, they aim to define the clinical, biochemical, structural, and metabolic presence of AD."

In an accompanying comment, Dr Norman Foster, Center for Alzheimer's Care, Department of Neurology, University of Utah, USA 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."
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Lancet

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