Diagnostic utility of Montreal Cognitive Assessment in the Fifth Edition of Diagnostic and Statistical Manual of Mental Disorders: major and mild neurocognitive disorders.

OBJECTIVES: The Montreal Cognitive Assessment (MOCA) is a screening tool for mild cognitive impairment (MCI) and dementia. The new criteria for Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition (DSM-5) mild neurocognitive disorder (NCD) define participants with cognitive decline but no dementia, and major NCD (dementia). We explored the usefulness of MOCA to detect major and mild NCD.

DESIGN: Cross-sectional test research.

SETTING: Tertiary hospital memory clinic and community-based Singapore Longitudinal Aging Study (SLAS).

PARTICIPANTS: Participants with questionable dementia (clinical dementia rating, CDR = 0.5) and early dementia (CDR ≤1) over a period of 1 year were identified from the memory clinic registry. The patient records were reviewed and the diagnostic labels of major and mild NCD were applied accordingly. Healthy controls (HC) (CDR = 0, Mini-Mental State Examination >26) were recruited from the on-going SLAS.

MEASUREMENTS: Major and mild NCD were diagnosed based on medical history, clinical examination, basic and instrumental activities of daily living, locally validated bedside cognitive tests (Mini-Mental State Examination, Frontal Assessment Battery, and Clock Drawing Test), relevant laboratory investigations and standardized neuropsychological assessment.

RESULTS: Two hundred fifty-one participants were included (41 mild NCD, 64 major NCD, 146 HC). On receiver operating characteristic curve analysis, the diagnostic performance by area under the curve (AUC) for MOCA was 0.99 [95% confidence interval (CI) 0.98-1.0] for major NCD and 0.77 (95% CI 0.67-0.86) for mild NCD. For diagnosis of mild NCD, MOCA performed better in those with lower education (primary and below) (AUC 0.90) compared with those with secondary education and beyond (AUC 0.66).

CONCLUSION: MOCA has high diagnostic utility for major NCD but its usefulness in detecting mild NCD is more modest. Possible reasons include greater heterogeneity in participants with mild NCD and how "quantified clinical assessment" in the DSM-5 mild NCD criteria is interpreted and operationalized.