Neuropsychological differentiation of small vessel disease, Alzheimer's disease and mixed dementia.

This study examined the neuropsychological profile of probable Alzheimer's disease (AD, n=72), vascular dementia due to diffuse subcortical small vessel disease (SVD, n=18) and mixed dementia (AD+SVD, n=18). Five simple tests were analysed, i.e. verbal recall and recognition memory, object naming, word fluency and clock reading. Pairwise discriminant analyses classified 79-83% of the cases correctly. Mixed dementia (MD) patients showed lower word fluency; otherwise, their profile was indistinguishable from AD. Recognition memory and clock reading were identified as predictors of SVD vs. AD diagnosis. The potential of single variables to distinguish the groups was tested by receiver operator characteristic curve analysis. A clock reading cut-off score close to maximum separated SVD from AD and MD. Recognition memory separated SVD from AD. These results show that neuropsychological tests can distinguish SVD and MD from AD with high sensitivity (88-94%). Due to the overlapping of scores and a higher prevalence of AD, specificity was moderate (65-76%) and positive predictive values were low, whereas sensitivity and negative predictive indices were high.