The purpose of this study was to analyse the validity of the five MoCA-BC items (verbal fluency, orientation, visual perception, immediate recall, and delayed recall) for screening cognitive impairment and the severity of cognitive impairment. The optimal cutoff of the five items in screening for MCI and AD was analysed, which is helpful for clinicians to more intuitively judge these five domains of cognitive impairment. We found that there were differences in age and gender among the four groups in the high-education level groups, and there was an extremely weak negative correlation between age and cognitive impairment, which is consistent with AD itself being an age-related disease. We used analysis of covariance in the high education level population, using age as a covariate to analyze and control the effect of age on the test results. After that, there were differences between the four groups. In China's epidemiological survey, women's cognitive impairment is slightly higher than that of men, and studies using multivariate analysis of age groups show that this difference is associated with lower education and chronic disease rates among women. Highly related, it is considered that gender has no significant effect on cognitive test scores.The level of education is considered to be the most important factor in cognitive testing (such as the MoCA and MMSE). The optimal cutoff scores for MCI or AD screening for cognitive impairment in China are different according to the level of education. Therefore, to reduce the influence of cultural bias on scores, this paper analyses the difference of the five item scores between NC, MCI, mild AD and severe-moderate AD according the educational level.
In our study, we found that among the NC, MCI, mild AD, and moderate-severe AD groups, there were differences in delayed recall, verbal fluency, visual perception, immediate recall, and orientation. These relations are similar to F. Clement’s research [17, 18] . Education had no effect on orientation and delayed recall. Our results showed that the orientation test was effective in identifying MCI, mild AD, and moderate to severe AD, but poor discrimination between MCI and NC. Memory impairment was the first impaired domain in MCI individuals who had less disruption in the orientation test [12, 19] . The orientation test was easy to complete and showed a ceiling effect when screening for NC and MCI. The delayed recall test has good validity in identifying NC, MCI, and mild AD groups, but no validity in distinguishing the severity of AD; this is probably owing to a floor effect, because in confirmed AD individuals, delayed recall memory impairment is too serious to complete the delayed recall test. However, when screening for MCI or AD, the AUC for the delayed recall test was the largest, which is more conducive to the early recognition of cognitive dysfunction in MCI or AD patients. This is similar to the previous studies by Lin Huang et al. The memory index score of the MoCA-BC had high sensitivity and specificity for MCI screening, while the non-memory index score of the MoCA-BC had similar effectiveness for discrimination among MCI, mild AD and moderate AD groups.
Our results showed that the verbal fluency test had validity not only in the MCI group but also in the mild and moderate-severe AD groups in the three education subgroups. Visual perception and immediate recall tests had validity for discrimination among the NC, MCI, mild AD, and moderate-severe AD groups only in the high-level education population, while in low- and middle-level education populations the two items had poor validity for screening those with MCI from NC. This may be due to the need for a high level of education to complete the two items and the lower impairment in visual perception and immediate recall in MCI individuals.
Cognitive impairment can be manifested in many aspects, such as memory, orientation, language, executive function, visual perception, calculation, attention, and information processing. The MoCA-BC is a quick, simple, and feasible assessment tool not only for doctors but also for outpatients. Each item in the MoCA-BC is independent, which reflects the characteristics of cognitive impairment of dementia in different stages. Sometimes, elderly people may have vision or hearing impairments, and only part of the test can be completed; therefore, a total score cannot be obtained. The MoCA-BC item score is a good complement for these people. The analysis of the differences between the item scores across groups with different levels of cognitive function is very helpful in distinguishing the types of cognitive dysfunction and determining the field of cognitive impairment. Through each item, we can observe the main areas of cognitive impairment and help identify the types of cognitive impairment, further distinguishing between the recognition of AD, Lewy body dementia, vascular dementia or depression.
Of course, the items of the MoCA-BC scale cannot fully satisfy the identification for the stage of AD, so the MoCA-BC needs to be complemented by a combination of more complicated neuropsychological tests.
In summary, the MoCA-BC is a comprehensive test that combines sub-items to identify early MCI patients and to identify the severity of dementia. This study observed differences in verbal fluency, visual perception, immediate memory, delayed memory, and orientation among the NC group, MCI group, mild AD group, and moderate-severe AD group. The results of the present study indicate that there is a need for further research on the difference in the item scores between those with AD, Lewy body dementia, vascular dementia and depression.
Conflict of Interest: None.