Diagnostic accuracy of the Montreal Cognitive Assessment (MoCA) for cognitive screening in old age psychiatry: Determining cutoff scores in clinical practice. Avoiding spectrum bias caused by healthy controls

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Abstract
Objective/Methods The Montreal Cognitive Assessment (MoCA) is an increasingly used screening tool for cognitive impairment. While it has been validated in multiple settings and languages, most studies have used a biased case‐control design including healthy controls as comparisons not representing a clinical setting. The purpose of the present cross‐sectional study is to test the criterion validity of the MoCA for MCI and mild dementia (MD) in an old age psychiatry cohort (n=710). The reference standard consists of a multidisciplinary, consensus‐based diagnosis in accordance with international criteria. As a secondary outcome the use of healthy community older adults as additional comparisons allowed us to underscore the effects of case‐control spectrum‐bias. Results The criterion validity of the MoCA for cognitive impairment (MCI+MD) in a case‐control design, using healthy controls, was satisfactory (AUC 0.93; specificity of 73% <26), but declined in the cross‐sectional design using referred but not cognitive impaired as comparisons (AUC 0.77; specificity of 37% <26). In an old age psychiatry setting the MoCA is valuable for: confirming normal‐cognition (≥26, 95% sensitivity), excluding MD (≥21;NPV 98%) and excluding MCI (≥26;NPV 94%); but not for diagnosing MD (<21;PPV 31%) or MCI (<26;PPV 33%). Conclusions This study shows that validating the MoCA using healthy controls, overestimates specificity. Taking clinical and demographic characteristics into account, the MoCA is a suitable screening tool – in an old age psychiatry setting – for distinguishing between those in need of further diagnostic investigations and those who are not, but not for diagnosing cognitive impairment.

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