A comparison of the Quick Dementia Rating System and Montreal Cognitive Assessment for detecting mild cognitive impairment and dementia assessed by the Clinical Dementia Rating Scale

Background The Clinical Dementia Rating (CDR) scale is widely used for staging mild cognitive impairment (MCI) and dementia but suffers from lengthy administration time (45–60 min). The Montreal Cognitive Assessment (MoCA; 10–15 min) and Quick Dementia Rating System (QDRS; 3–5 min) are promising brief alternatives, although it remains unclear which tool performs better in discriminating between cognitive and functional impairment stages. Objective To compare the performance of the QDRS and MoCA in identifying MCI, dementia, and individuals eligible for disease modifying therapies and clinical trials (DMTT). Methods 376 older adults (34.8% NCI, 33.0% MCI, 32.2% dementia) recruited from the memory clinic (n = 284, 75.5%) and community (n = 92, 24.5%) in Singapore completed the QDRS, MoCA, and CDR. No cognitive impairment (NCI), MCI, and dementia were staged as CDR-Global Scores (CDR-GS) of 0, 0.5, and ≥1, respectively. The DMTT subgroup was defined as CDR-GS of 0.5–1. Discriminative performance was determined by area under the curve (AUC) and compared using DeLong's test. Agreement with CDR classifications was determined on McNemar's test. Results Both QDRS and MoCA demonstrated fair-to-excellent discrimination across CDR-staged groups (MCI: AUC 0.79–0.84; Dementia: AUC 0.92–0.97; DMTT: AUC 0.85–0.91), with no significant differences in discrimination observed. The QDRS correctly identified a greater proportion of MCI (55.6% versus 19.4%; p < 0.001) and DMTT (58.9% versus 41.7%; p < 0.001) versus the MoCA. Conclusions The QDRS and MoCA are practical brief alternatives to the CDR. The QDRS was advantageous for identifying MCI and DMTT, whereas both were effective screening tools for dementia.