Cognistat reference scores in Alzheimer's disease at different levels of severity

The current study examined Cognistat scores in a large sample of Alzheimer's disease (AD) patients referred to a university-based research and diagnostic center for a complete dementia evaluation. Archival data were collected from 90 autopsy confirmed cases and 117 participants with a clinical diagnosis of AD. The final sample consisted of 62 autopsy confirmed and 57 probable AD cases that meet all inclusionary criteria. This study compared these two groups using a MANCOVA with the Mini-Mental State Examination (MMSE) score as the covariate. As predicted, the two groups were not statistically different from one another after controlling for MMSE. Subgroups were then created based on dementia severity. Reference scores consisting of means and standard deviations were obtained for the mild, moderate, and severe AD groups. The results of a MANOVA demonstrated that the performances on the Cognistat across severity levels were statistically different from one another. Post hoc analyses demonstrated statistically significant differences between the mild and moderate groups on the orientation subscale. No other statistical differences were found between these two groups. Statistically significant differences were found between the mild and severe group and the moderate and severe group on 9 of 10 subscales. Limitations and directions for future research are discussed.