Montreal Cognitive Assessment - Single Cutoff Achieves Screening Purpose.

BACKGROUND AND PURPOSE

The study evaluated the performance between norm-derived age and education adjusted vs single cutoff scores of the Montreal Cognitive Assessment, Hong Kong version (HK-MoCA) in classifying cognitive impairment in Chinese older adults.

METHODS

Total scores of HK-MoCA were collected from 315 subjects (128 with dementia, 122 with mild cognitive impairment (MCI) and 65 normal) attending a public district hospital-based cognition clinic from 2012 to 2017. The HK-MoCA total scores were evaluated using different cutoffs. Norm-derived age and education adjusted cutoff scores were at 16th, 7th, and 2nd percentiles. Comparison was made with the single cutoff scores validated in a local study with 21/22 for MCI and 18/19 for dementia.

RESULTS

Single cutoff score of HK-MoCA differentiated MCI from normal with sensitivity of 0.861 and specificity of 0.723. To detect dementia, its sensitivity was 0.922, and specificity was 0.923. In identifying cognitive impairment, the sensitivity and specificity were 0.932 and 0.723, respectively. However, age and education adjusted cutoff scores achieved high specificities at all levels of cognitive impairment with trade-off of sensitivities. The accuracy of correctly classifying tested subjects into appropriate groups was 85.3% if single cutoff was used though the consistency between norm-derived cutoffs and expert diagnoses were only 59.0%, 54.2%, and 53.9% at 16th, 7th, and 2nd percentiles, respectively. The consistency decreased with older age and lower education level, and majority of misclassifications were false negatives.

CONCLUSION

HK-MoCA is a convenient screening tool to detect cognitive impairment. Administration time is relatively short, and it has incorporated essential cognitive domains. Single cutoff scores with inherent simple education adjustment achieved screening purpose of mild cognitive impairment and dementia in Chinese older adults.