Are the indices of the RBANS sufficient for differentiating Alzheimer's disease and subcortical vascular dementia?

Alzheimer's disease (AD) and subcortical vascular dementia (SVaD) are among the most prevalent dementias and they often show specific patterns of cognitive dysfunction. This study examined whether differences exist between groups on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) that could assist with differential diagnosis. The examiners utilized the NINCDS-ADRDA and the NINDS-AIREN criteria to identify 39 probable AD and 29 probable SVaD patients. A battery of neuropsychological tests was performed and neuroimaging was reviewed for all subjects. Analyses revealed that the SVaD group performed significantly better on the Delayed Memory Index (DMI) and its subtests measuring Recognition, Contextual Memory, and Figure Recall. In contrast to previous research, there were no differences between groups on immediate memory tasks, and post hoc analyses revealed no differences on any other index or subtest. The results also suggested that the DMI and its subtests and the Story Memory subtest of the Immediate Memory Index have better sensitivity to AD, better specificity to SVaD, and roughly equivalent positive predictive power compared with other components of the RBANS. Overall, findings suggest that the indices and subtests of the RBANS may be limited in differentiating AD versus SVaD, except for the DMI and its subtests.