Care partner-informed meaningful change thresholds for the Clinical Dementia Rating-Sum of Boxes for trials of early Alzheimer's disease.

Introduction: Consensus definitions of meaningful within-patient change (MWPC) on the Clinical Dementia Rating-Sum of Boxes (CDR-SB) are needed. Existing estimates use clinician-rated anchors in clinically diagnosed Alzheimer's disease (AD) populations. Incorporating the care partner perspective offers important insights, and evaluating biomarker-confirmed cohorts aligns estimates with ongoing trials.

Methods: Anchor-based analyses were conducted to evaluate MWPC on the CDR-SB in early AD (Tauriel; NCT03289143) using Caregiver Global Impression of Change in memory or daily activities.

Results: Across time points and anchors, mean CDR-SB changes associated with the "somewhat worse" category ranged from 1.50 to 2.12 in early AD, 1.07 to 2.06 in mild cognitive impairment-AD, and 1.79 to 2.25 in mild AD.

Discussion: The proposed ranges are appropriate to define meaningful progression on the CDR-SB in similar cohorts and support the interpretation of treatment benefit through MWPC analyses. Thresholds should be calibrated to the context of use; lower/higher thresholds may be applicable in studies of earlier/later disease over shorter/longer durations.

Highlights: Within-patient CDR-SB change thresholds are provided using caregiver-rated anchors. 1.5 to 2.5 points may be an appropriate range in early AD trials of similar durations. Cumulative distribution function plots illustrate the benefit of a given treatment. When selecting thresholds, the target population and study design should be considered.