Questionable dementia: Clinical course and predictors of outcome

OBJECTIVE: To evaluate the clinical course and predictors of outcome in outpatients with cognitive impairment who do not meet criteria for dementia at initial evaluation. DESIGN: Naturalistic longitudinal study. METHODS: Cognitively impaired patients in a memory disorders clinic who fell between the ''normal'' and ''dementia'' categories were defined broadly as ''questionable dementia'' (QD). Of 127 consecutive QD patients, 75 were followed for a minimum of 1 year (mean 2.5 years, SD 1.7). Baseline neuropsychological testing was conducted in 62 of these 75 QD patients. RESULTS:: At the final follow-up time-point, 41.3% met diagnostic criteria for dementia 127 of 31 patients with dementia had possible or probable Alzheimer's Disease, AD), 44% were rated as not demented, and 14.7% remained as ''uncertain'' dementia. Increased age was associated with the final diagnosis of dementia, but duration of follow-up, Clinical Dementia Rating, and modified Mini Mental State (mMMS) scores were not predictive. Low scores on the mMMS delayed recall subtest, consistent long-term retrieval on the Selective Reminding Test, category naming for animars, and the WAIS-R digit symbol, picture arrangement, and block design subtests were predictive of the final diagnosis of dementia (all P less than or equal to 1.01). mMMS delayed recall showed 66.7% sensitivity and 71.4% specificity, the other five neuropsychological subtests together showed 66.7% sensitivity and 66.7% specificity, and the six tests together showed 81% sensitivity and 76.9% specificity. Similar predictive accuracy was obtained for the final diagnosis of AD. CONCLUSIONS: In QD patients, poor performance on the mMMS delayed recall item may be a useful predictor of the diagnosis of dementia (and AD) on follow-up. Combining a screening instrument like the mMMS with specific neuropsy-chological tests may provide good predictive accuracy. In QD patients, the observed heterogeneity in diagnostic outcome, with most patients in the ''dementia'' and ''no dementia'' categories at follow-up, enhances the feasibility of evaluating early markers with predictive accuracy for dementia and AD.