"(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," says Dr. Bruno Dubois, Salpetriere Hosptial, Paris, France.
According to experts, the new criteria for probable AD requires that patients show progressive memory loss over more than six months, and at least one or more of the supportive biomarker criteria-like 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.
"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," say the authors, whose proposal is put forward in a Position Paper published in The Lancet Neurology.
The researchers, however, admit that validation studies are required to advance the new criteria and optimise their sensitivity, specificity and accuracy.
"When effective disease-modifying medications are available, the argument for such biologically based studies will be even more compelling," conclude the authors.
"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," they say.
Dr Norman Foster, Center for Alzheimer's Care, Department of Neurology, University of Utah, US, feels that it is time that advanced technologies be involved in the diagnosis of AD.
"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," says the researcher.
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.