Development of a rapid screening instrument for mild cognitive impairment and undiagnosed dementia

Abstract

Mild cognitive impairment (MCI) often presages development of Alzheimer's disease (AD). We recently completed a cross-sectional study to test the hypothesis that a combination of a brief cognitive screening instrument (Mini-Cog) with a functional scale (Functional Activities Questionnaire; FAQ) would accurately identify individuals with MCI and undiagnosed dementia. The Mini-Cog consists of a clock drawing task and 3-item recall, and takes less than 5 minutes to administer. The FAQ is a 30-item questionnaire completed by an informant. In addition to the Mini-Cog and FAQ, a traditional cognitive test battery was administered, and two neurologists and a neuropsychologist determined a consensus diagnosis of Normal, MCI, or Dementia. A classification tree algorithm was used to pick optimal cutpoints, and, using these cutpoints, the combined Mini-Cog and FAQ (MC-FAQ) predicted the consensus diagnosis with an accuracy of 83% and a weighted kappa of 0.81. When the population was divided into Normal and Abnormal, the sensitivity, specificity and positive predictive value were 89%, 90%, and 95%, respectively. The MC-FAQ discriminates individuals with MCI from cognitively normal individuals and those with dementia, and its ease of administration makes it an attractive screening instrument to aid detection of cognitive impairment in the elderly.

Fig. 1

A. Distribution of cases along functional (FAQ) and cognitive (Mini-Cog) axes. Classification based on the MC-FAQ screener can be read off of a simple grid. Cases falling within white cells are Normal, those in gray cells are MCI, and those in black cells are Dementia. B. Distribution of cases along functional (FAQ) and cognitive (MMSE) axes. Cases falling within white cells are Normal, those in gray ells are MCI, and those in black cells are Dementia.