Amnestic mild cognitive impairment: diagnostic outcomes and clinical prediction over a two-year time period

Abstract

Amnestic mild cognitive impairment (MCI) has been defined as a precursor to Alzheimer's disease (AD), although it is sometimes difficult to identify which persons with MCI will eventually convert to AD. We sought to predict MCI conversion to AD over a two-year follow-up period using baseline demographic and neuropsychological test data from 49 MCI patients. Using a stepwise discriminant function analysis with Dementia Rating Scale (DRS) Initiation/Perseveration and Wechsler Memory Scale, third edition (WMS-III) Visual Reproduction Percent Retention scores, we correctly classified 85.7% of the sample as either AD converters or MCI nonconverters, with 76.9% sensitivity and 88.9% specificity. Adding race, the presence of vascular risk factors, or cholinesterase inhibitor use to the analysis did not greatly change the classification rates obtained with neuropsychological test data. Examining neuropsychological test cutoff scores revealed that DRS Initiation/Perseveration scores below 37 and Visual Reproduction Percent Retention scores below 26% correctly identified AD converters with 76.9% sensitivity and 91.7% specificity. These results demonstrate that commonly administered neuropsychological tests identify persons with MCI at baseline who are at risk for conversion to AD within 1-2 years. Such methods could aid in identifying MCI patients who might benefit from early treatment, in providing prognostic information to patients, and identifying potential clinical trial participants.