[The new 2011 recommendations of the National Institute on Aging and the Alzheimer's Association on diagnostic guidelines for Alzheimer's disease: Preclinal stages, mild cognitive impairment, and dementia]

Abstract

Background: Criteria for the clinical diagnosis of Alzheimer's disease (AD) were established in 1984, and they needed to be updated and revised, in vue of the scientific knowledge acquired over the last decades.

Methods: The National Institute on Aging (NIA) and the Alzheimer's Association (AA) sponsored a series of advisory round table meetings to establish a revision of diagnostic and research criteria for AD. The workgroups reviewed the biomarker, epidemiological, and neuropsychological evidence, and proposed conceptual frameworks as well as operational research criteria based on the prevailing scientific evidence to date.

Results: Three preclinical stages of AD were proposed: asymptomatic amyloidosis, asymptomatic amyloidosis+neurodegeneration, amyloidosis+neurodegeneration+subtle cognitive decline. The preclinical workgroup developed recommendations to determine the factors, which best predict the risk of progression from normal cognition to mild cognitive impairment (MCI) and AD dementia. It is necessary to refine these models with longitudinal clinical research studies. The workgroups on MCI and AD dementia sought to ensure that the revised criteria would be flexible enough to be used by both general healthcare providers without access to neuropsychological testing, advanced imaging, and cerebrospinal fluid measures, and specialized investigators involved in research or in clinical trial studies who would have these tools available. The symptomatic predementia phase of AD was referred to as MCI due to AD. Core clinical and cognitive criteria of MCI were proposed, the final set of criteria for MCI due to AD has four levels of certainty, depending on the presence and nature of the biomarker findings. Criteria for all-cause dementia and for AD dementia were presented. Dementia caused by AD were classified in: probable AD dementia, possible AD dementia, and probable or possible AD dementia with evidence of the AD pathophysiological process, for use in research settings. The core clinical criteria for AD dementia will continue to be the cornerstone of the diagnosis in clinical practice, but biomarker evidence is expected to enhance the pathophysiological specificity of the diagnosis.

Conclusions: In the revised criteria, a conceptual distinction is made between AD pathophysiological processes and clinically observable syndromes. The core clinical criteria of the recommendations regarding MCI due to AD and AD dementia are intended to guide diagnosis in the clinical setting whereas the recommendations of the preclinical AD workgroup are intended purely for research purposes and do not have any clinical implications. Considerable work is needed to validate the criteria that use biomarkers and to standardize biomarker analysis for use in community settings.