High specificity of MMSE pentagon scoring for diagnosis of prodromal dementia with Lewy bodies

Background Patients with dementia with Lewy bodies (DLB) may display a different cognitive pattern from Alzheimer's disease (AD) with more severe impairment performing visuospatial/visuoconstructive tasks. The aim of this study was to investigate whether the analysis of the MMSE pentagon copy could be a useful diagnostic screening tool in prodromal DLB. Methods Fifty-three patients with Mild Cognitive Impairment (MCI) were followed over 3-years until a diagnosis of DLB (MCI–DLB: n = 30) and AD (MCI–AD: n = 23) were made according to standard criteria. At the first assessment patients underwent a thorough cognitive assessment including the Qualitative Scoring MMSE Pentagon Test (QSPT), the NPI, the UPDRS as well as questionnaires to determine fluctuations and sleep disorders. Results The percentage of subjects who were unable to determine the correct number of angles in the pentagon copy test was 45.1% of MCI–DLB and 8.3% of MCI–AD patients (sensitivity 41.1%; specificity 91%). Attentive/executive functions and visual-spatial abilities were worse in the MCI–DLB group, while episodic memory impairment was greater in MCI–AD. Subtle extrapyramidal signs (63%) and RBD symptoms (56%) were the most frequent clinical features supporting the diagnosis of MCI–DLB. Conclusions We suggest that a poor performance in determining the number of angles when performing the pentagon copying test, together with the presence of subtle extrapyramidal signs and symptoms of RBD may serve as a predictive tool for early DLB.