Reliability and validity of A Quick Test of Cognitive Speed for detecting early-stage dementia in elderly Japanese.

AIM: The aim of this study was to evaluate the reliability and validity of A Quick Test of Cognitive Speed (AQT) for detecting early-stage dementia in the elderly Japanese population.

METHODS: A total of 280 clinical participants (180 with mild Alzheimer's disease, 43 with amnestic mild cognitive impairment, 32 with non-amnestic mild cognitive impairment and 25 control subjects) and 22 community-dwelling elderly individuals without dementia were recruited. The Clinical Dementia Rating, the Mini-Mental State Examination, and AQT were administered to all participants. The Neurobehavioral Cognitive Status Examination was also administered to clinical participants.

RESULTS: The intraclass correlation coefficient for the test-retest reliability of colour-form naming time on AQT was 0.88 (95% CI, 0.74-0.95, P < 0.001). AQT colour-form naming time was significantly correlated with the Clinical Dementia Rating, the total score on the Mini-Mental State Examination, and the total score on the Neurobehavioral Cognitive Status Examination and most of its subscales. AQT colour-form naming time was significantly longer in elderly individuals with mild Alzheimer's disease, amnestic mild cognitive impairment, and non-amnestic mild cognitive impairment than in control subjects. The receiver operating characteristic curve analysis indicated that AQT colour-form naming time significantly distinguished subjects with early-stage dementia (mild Alzheimer's disease, amnestic mild cognitive impairment, and non-amnestic mild cognitive impairment) from controls. The area under the curve was estimated to be 0.88 (95%CI = 0.82-0.95). A cut-off of 71/72 seconds yielded the best sensitivity/specificity trade-off: sensitivity = 85% and specificity = 76%.

CONCLUSIONS: AQT is a useful brief screening tool for detecting early-stage dementia in elderly Japanese individuals.