The Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) is a renowned cognitive test battery, which has been extended in its German version to the CERAD-Plus including tests of executive functions and processing speed. The most commonly used total score (TS) is based on the restricted CERAD version and reflects the sum of selected raw-values (Chandler et al., 2005). The CERAD-Plus extensions might be of particular diagnostic utility for cognitive assessments in Parkinson’s Disease (PD), as executive functions and processing speed belong to the most vulnerable domains in PD.
The aim was to develop a CERAD-TS based on the extended CERAD-Plus’ age-, gender-, and education-corrected z-scores and to evaluate its diagnostic accuracy compared to the established CERAD-Chandler-TS.
Baseline data of n = 679 patients with PD (69% male, n = 277 PD without cognitive impairment, n = 307 PD-MCI, n = 95 PD-D) from the multicenter, prospective DEMPARK/LANDSCAPE study were analyzed. ROC-analyses were conducted for four different TS that were either based on the original CERAD or CERAD-Plus, on raw-values or z-scores, and equally-weighted or based on factor scores. AUC-comparisons were conducted to determine the best yet most parsimonious TS.
The newly designed CERAD-Plus-TS based on equally-weighted z-scores outperformed both the CERAD-Chandler-TS and cognitive screening instruments when differentiating between individuals with PD of varying cognitive impairment (0.78 ≤ AUC ≤ 0.98).
Results suggest a high relevance of non-amnestic subscales for the cognitive assessment in PD populations. The proposed CERAD-Plus-TS needs further validation. The extensions might offer diagnostic potential for non-PD populations as well.