February 7, 2012
Revised Criteria Could Reclassify Many With Mild Alzheimer Dementia
Many patients currently diagnosed with very mild or mild Alzheimer disease dementia could potentially be reclassified as having mild cognitive impairment (MCI) under revised criteria for that condition, according to a report published Online First by Archives of Neurology, one of the JAMA/Archives journals.
The National Institute on Aging and the Alzheimer's Association convened a work group to update criteria for MCI, and the revised criteria allow "considerable latitude" as to what represents functional independence, writes the study's sole author, John C. Morris, M.D., of Washington University School of Medicine in St. Louis. For example, "mild problems" performing daily activities such as shopping, paying bills and cooking are permissible, as is dependency on aids or assistance to complete those tasks.In this study, the functional ratings of patients enrolled at federally funded Alzheimer's Disease Centers with clinical and cognitive data maintained by the National Alzheimer's Coordinating Center were evaluated. A total of 17,535 people with normal cognition, MCI or AD dementia met eligibility requirements. The mean (average) age of the total sample was 74.6 years.
The study suggests that 99.8 percent of patients currently diagnosed with very mild AD dementia and 92.7 percent of those diagnosed with mild AD dementia could be reclassified as having MCI based on the revised criteria.
The difference between MCI and AD dementia in its earliest symptomatic stages has largely been based on whether cognitive impairment disrupts the activities of daily living. The revised criteria "now obscure this distinction," Morris notes.
"The elimination of the functional boundary between MCI and AD dementia means that their distinction will be based solely on the individual judgment of clinicians, resulting in nonstandard and ultimately arbitrary diagnostic approaches to MCI," Morris comments. "This recalibration of MCI moves its focus away from the earliest stages of cognitive decline, confounds clinical trials of individuals with MCI where progression to AD dementia is an outcome, and complicates diagnostic decisions and research comparisons with legacy data."
The author suggests that the revised criteria for MCI "laudably recommend" an etiologic (origins) diagnosis, "MCI due to AD," when the physician's judgment is that AD is responsible for an individual's cognitive dysfunction.
"The diagnostic overlap for MCI with milder cases of AD dementia is considerable and suggests that any distinction is artificial and arbitrary," Morris concludes. "Already, many individuals with MCI are treated with pharmacological agents approved for symptomatic AD, indicating that clinicians often do not distinguish the two conditions when faced with issues of medical management. It now is time to advance AD patient care and research by accepting that 'MCI due to AD' is more appropriately recognized as the earliest symptomatic stage of AD."
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