The revised Addenbrooke's Cognitive Examination can facilitate differentiation of dementia with Lewy bodies from Alzheimer's disease

Objectives Dementia with Lewy bodies (DLB) is a major cause of degenerative dementia, yet the diagnosis is often missed or mistaken for Alzheimer's disease (AD). We assessed whether the revised Addenbrooke's Cognitive Examination (ACE-R), a brief test for dementia, differentiates DLB from AD. Methods We first compared baseline ACE-R performance in 76 individuals with DLB, 40 individuals with AD and 66 healthy controls. We then investigated the diagnostic accuracy of a simple standardised 'memory/visuospatial' ratio calculated from the ACE-R subscores. Finally, as a comparison a logistic regression machine learning algorithm was trained to classify between DLB and AD. Results Individuals with AD had poorer memory (p = 0.001) and individuals with DLB had poorer visuospatial function (p = 0.005). Receiver operating characteristics curves confirmed that the ACE-R total score could differentiate dementia from non-dementia cases with 98% accuracy, but could not discriminate between dementia types (50%, or chance-level accuracy). However, a 'memory/visuospatial' ratio >= 1.1 differentiated DLB from AD with 82% sensitivity, 68% specificity and 77% mean accuracy. The machine learning classifier did not improve the overall diagnostic accuracy (74%) of the simple ACE-R subscores ratio. Conclusions The ACE-R-based 'memory/visuospatial' ratio, but not total score, demonstrates good clinical utility for the differential diagnosis of DLB from AD.