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disease experts are proposing new ways to diagnose the neurological condition, arguing that the existing criteria are out of date.

Alzheimer's disease 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 to 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 diagnostic 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. "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."

ABSTRACT

Research criteria for the diagnosis of Alzheimer's disease: revising the NINCDS-ADRDA criteria

Bruno Dubois MD, Howard H Feldman MD, Claudia Jacova PhD, Steven T DeKosky MD, Pascale Barberger-Gateau MD, Jeffrey Cummings MD, Andr¨¦ Delacourte PhD, Douglas Galasko MD, Serge Gauthier MD, Gregory Jicha MD, Kenichi Meguro MD, John O'Brien MD, Florence Pasquier MD, Philippe Robert MD, Martin Rossor MD, Steven Salloway MD, Yaakov Stern PhD, Pieter J Visser MD and Philip Scheltens MD

The NINCDS-ADRDA and the DSM-IV-TR criteria for Alzheimer's disease (AD) 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. This progress provides the impetus for our proposal of revised diagnostic criteria for AD.

Our framework was developed to capture both the earliest stages, before full-blown dementia, as well as the full spectrum of the illness. These new criteria are centred on a clinical core of early and significant episodic memory impairment. They stipulate that there must also be at least one or more abnormal biomarkers among structural neuroimaging with MRI, molecular neuroimaging with PET, and cerebrospinal fluid analysis of amyloid beta or tau proteins.

The timeliness of these criteria is highlighted by the many drugs in development that are directed at changing pathogenesis, particularly at the production and clearance of amyloid beta as well as at the hyperphosphorylation state of tau.

Validation studies in existing and prospective cohorts are needed to advance these criteria and optimise their sensitivity, specificity, and accuracy.

• Full text in The Lancet Neurology (requires subscription)