The severe cognitive impairment rating scale - An instrument for the assessment of cognition in moderate to severe dementia patients

Background/Aims: This study aimed to develop a brief, reliable and valid test for cognitive function of severely demented patients. Methods: We constructed the Severe Cognitive Impairment Rating Scale, which consisted of 11 items covering memory, language, visuospatial function, frontal function and orientation, and investigated its reliability and validity on 267 subjects [ normal: 65, very mild Alzheimer's disease (AD): 42, mild AD: 58, moderate AD: 36, severe AD: 44, profound AD: 22]. Results: The internal consistency obtained by Cronbach's coefficient alpha was 0.93. The interrater reliability and test-retest reliability in the moderately to severely impaired subjects with an MMSE score of <= 14 was 0.99 (p < 0.001) and 0.90 (p < 0.001), respectively. It showed significant correlation with Severe MMSE (r = 0.96, p < 0.01), MMSE (r = 0.86, p < 0.01) and Clinical Dementia Rating (r = -0.83, p < 0.01). It was robust to both the floor effect in the severe/profound stage of AD and the ceiling effect in the mild/moderate stage of AD. Exploratory factor analysis yielded 2 factors (automatic informational processing and controlled informational processing) accounting for 73.5% of the total variance. Conclusions: The Severe Cognitive Impairment Rating Scale is a valid and reliable test for evaluating the cognitive function of advanced AD patients. Copyright (C) 2008 S. Karger AG, Basel.