Criteria updated in diagnosis of Alzheimer's disease

July 15, 2011

According to new guidelines, researchers at the Alzheimer's Association and the National Institute of Aging of the National Institutes of Health have categorized AD into 3 different stages: preclinical, mild cognitive impairment, and Alzheimer's dementia.

Key Points

New guidelines designed to support earlier detection and diagnosis of Alzheimer's disease (AD) recently were released. Rsearchers at the Alzheimer's Association and the National Institute of Aging of the National Institutes of Health have categorized AD into 3 different stages: preclinical, mild cognitive impairment (MCI), and Alzheimer's dementia.1

Preclinical stage

One workgroup focused on the preclinical stage of Alzheimer's disease. Researchers suggested that brain changes rather than symptomatic manifestations occur during this stage. Amyloid beta (Aß) is believed to be the earliest biomarker that can be used when evaluating patients for possible AD. The amyloid buildup can be identified with positron emission topography (PET) scans and cerebrospinal fluid (CSF) analysis.

Mild cognitive impairment

The workgroup charged with developing criteria for MCI resulting from AD provided 2 sets of criteria. The first can be used in the clinical setting by practitioners without access to advanced technology; the second set is used in research settings.3

Researchers suggested that individuals with MCI present with changes in cognition, but their cognition is not impaired enough to constitute dementia. Such patients commonly display lower performance in 1 or more cognitive domains (memory, executive function, attention, language, or visuospatial skills) that is greater than expected in light of the patients' ages and educational backgrounds.3

Concerning research criteria, the guideline focused on the role of biomarkers, including Aß and tau. CSF with low Aß42 levels and PET amyloid imaging are used as markers for Aß deposition. Elevated levels of CSF tau indicate neuronal injury, signaling progression toward MCI and eventually AD.3

Dementia

Another workgroup developed 2 sets of criteria for determining AD dementia, dividing them between all-cause dementia and dementia caused by AD, and outlining an approach to a patient with possible dementia through evaluation of the causes and progression of cognitive decline.

Previously AD focused on memory loss. The new guidelines expand the criteria to include lack of ability to function in usual activities, decline from levels of functioning, and cognitive and behavioral impairment in 2 or more prespecified domains such as impaired reasoning and impaired ability to remember new information.

The criteria for dementia caused by AD incorporated new classification terminology: probable AD dementia, possible AD dementia, and probable or possible AD dementia with evidence of the AD pathophysiological process. Researchers described specific characteristics that patients would present in each of these categories.

The new criteria incorporated biomarkers in the diagnosis of AD for use in research settings, as well as for aiding in the diagnosis of AD versus other types of dementia. At this stage, the biomarkers are not yet standardized to a degree that would allow their use in diagnosis.4

References

Citations taken from Recommendations from the National Institute on Aging – Alzheimer's Association workgroups on diagnostic guidelines for Alzheimer's disease. Alzheimer's & Dementia: The Journal of the Alzheimer's Association. 2011; 7(3).

1. Jack CR, Albert MS, Knopman DS, et al. Introduction, pp. 257–262.

2. McKhann GM, Knopman DS, Chertkow H, et al. The diagnosis of dementia due to Alzheimer's disease, pp. 263–269.

3. Albert MS, DeKosky ST, Dickson D, et al. The diagnosis of mild cognitive impairment due to Alzheimer's disease, pp. 270–279.

4. Sperling RA, Aisen PS, Beckett LA, et al. Toward defining the preclinical stages of Alzheimer's disease, pp. 280–292.

Kimberly Ng and Kimberly Vo are PharmD candidates at St. John's University, Queens, N.Y., where Maha Saad is assistant clinical professor in the College of Pharmacy and Allied Health Professions.