A panel of researchers from the National Institutes of Health and the Alzheimer’s Association has revised the clinical diagnostic criteria for Alzheimer disease for the first time in 27 years.
Published in 1984, the first-ever clinical description of Alzheimer disease (AD) defined the illness as a single stage of dementia, with diagnosis based solely on clinical symptoms.
The new National Institute on Aging/Alzheimer’s Association Diagnostic Guidelines for Alzhemier’s Disease and Alzheimer’s Dementia cover three distinct phases of disease and address the use of imaging and biomarkers in both academic and clinical settings.
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“Alzheimer’s research has greatly evolved over the past quarter of a century. Bringing the diagnostic guidelines up to speed with those advances is both a necessary and rewarding effort that will benefit patients and accelerate the pace of research,” Richard J. Hodes, MD, director of the National Institute on Aging, said in a press release.
The revised guidelines feature three main sections, presided over by three distinct panels of researchers that make up one Alzheimer’s Association workgroup.
The most relevant section of the guidelines for clinicians and patients focuses on the final stages of AD dementia. Guy M. McKhann, MD of the Johns Hopkins University School of Medicine in Baltimore and David S. Knopman, MD, of the Mayo Clinic in Rochester, Minn., co-chaired the dementia panel, which outlined clinical approaches for evaluating the causes and progression of cognitive decline.
McKahnn and colleagues decided to retain the general framework of AD dementia from the 1984 criteria, but worked to expand the concept beyond memory loss to include declines in other aspects of cognition, some of which are the first signs of the disease. These include: word finding, vision/spatial issues, and impaired reasoning or judgment. Other key changes include a more detailed explanation of the term possible AD dementia.
Although biomarker tests are still investigational, the panel recognized that these tools could still be valuable in everyday clinical practice in some cases to increase or decrease the level of certainty about an AD dementia diagnosis.
Reisa A. Sperling, MD, of Harvard Medical School in Boston, and colleagues developed separate criteria for preclinical stages of the disorder that describe the early brain changes associated with AD.
Primarily intended for use in academic research settings, this section of the guidelines includes information on amyloid plaque buildup, which can occur 10 years or more before clinically significant symptoms appear. The panel explained that although amyloid deposits form early in the disease and can be detected with PET scans and cerebrospinal fluid analysis, a patient’s risk for progression to AD dementia may vary.
Marilyn Albert, PhD, of Johns Hopkins School of Medicine, headed the panel on mild cognitive impairment (MCI), a “symptomatic pre-dementia stage” of the disease marked by noticeable symptoms of memory problems that do not yet compromise a person’s independence.
This section of the guidelines defines specific AD biomarkers, such as increased tau levels and decreased beta-amyloid in cerebrospinal fluid, as well as levels of certainty for each biomarkers use in diagnosing AD-associated MCI in research settings.
It also clarifies existing guidelines for MCI in clinical settings in which health care providers do not have access to advanced imaging techniques or cerebrospinal fluid testing, and includes specific terminology to help clinicians classify patients with MCI who are at various risks for AD.
“The workgroup sought to insure that the revised criteria would be flexible enough to be used by both general health care providers without access to neurophysiological 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 workgroup wrote.
The full guidelines were published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, and can be accessed, here.
