Bridging the gap: A conversion framework for CDR-SB and MoCA scores in Alzheimer's disease and related dementia

Accurate assessment of cognitive impairment is essential to effective Alzheimer's disease (AD) management and research. However, the absence of validated methods to translate scores between widely used instruments-such as the Clinical Dementia Rating Scale Sum of Boxes (CDR-SB) in trials and the Montreal Cognitive Assessment (MoCA) in clinical practice-poses a significant barrier. This limits data harmonization, impedes cross-study comparability, and complicates the integration of clinical and research evidence. Bridging this gap is critical for consistent staging, longitudinal monitoring, and data-driven decision-making in AD and related dementias.

To develop and validate bidirectional score conversion tables between CDR-SB and MoCA using a large, diverse cohort spanning the full spectrum of cognitive function.

Retrospective, cross-sectional analysis using equipercentile equating with log-linear smoothing. Optimal smoothing parameters were selected by minimizing mean squared error, Akaike Information Criterion, and Bayesian Information Criterion. Concordance was assessed using Spearman's rank correlation and Bland-Altman plots.

National Alzheimer's Coordinating Center (NACC), aggregating standardized assessments from 35 U.S.-based Alzheimer's Disease Research Centers.

23,717 individuals (59,871 visits) with same-day CDR-SB and MoCA assessments from January 2015 to September 2024, spanning normal cognition, mild cognitive impairment (MCI), and dementia.

None; this was a secondary analysis of existing data.

Primary measures included CDR-SB (0-18; higher = greater impairment) and MoCA (0-30; higher = better cognition). Bidirectional crosswalk tables were derived using equipercentile equating.

CDR-SB and MoCA scores showed strong inverse correlation (Spearman's ρ = -0.68; p < 0.001). Crosswalk tables demonstrated good agreement across the cognitive spectrum and performed consistently in the full cohort and an AD-specific subgroup.

This study provides the first validated, bidirectional CDR-SB-MoCA crosswalk, supporting data harmonization and consistent interpretation of cognitive severity across research and clinical settings.