A quick test of cognitive speed in older adults with Alzheimer's disease and mild cognitive impairment: A preliminary behavioral and brain imaging study

The purpose of this study was to assess scores and processing speed distributions of the instrument, A Quick Test of Cognitive Speed (AQT), in Korean older adults through behavioral and brain imaging approaches. Participants were instructed to say the color names, stimuli's form, and both the color and form. Test scores and processing speeds were measured in these three subtests of color, form, and color-form. A total of 67 patients (22 healthy controls (HC), 22 with mild cognitive impairment (MCI), and 23 with Alzheimer's disease (AD)) participated. Only color-form score and processing speed of the three subtests could be used to differentiate AD from MCI and HC. Color-form score showed the largest effects size (partial eta(2) = 0.268) for distinguishing AD, MCI from HC and ROC curve analysis confirmed a high level of sensitivity (0.857) and specificity (0.826) for discrimination between AD and HC. None of the subtests could differentiate HC from MCI. Voxel-based morphometry analysis of brain structure in 27 participants (9 in each group) revealed that gray matter volume of the middle occipital gyrus and inferior parietal cortex were associated with color-form score. This study suggests preliminary evidence in the clinical utility of the AQT for screening AD in older Korean adults. The color-form score could be implemented for clinical utilization in a very brief time. Furthermore, strong positive correlations between color-form scores and the brain areas responsible for visuospatial working memory corroborate the validity of AQT.