Research Of The Differences Of Performance Between All Kinds Of Error Types In Qualitative Analysis Of The Clocku Drawing Test(CDT)in Terms Of Dementia Subtypes And Severity

Background and objectiveDementia is a group of diseases which affect all aspects of cognitive function. With rising incidence in recent years, it has caused heavy financial and emotional burden to patients and caregivers. Although the current medical technology can’t reverse the occurrence of dementia, early diagnosis and intervention can effectively slow the progression of dementia in the course. Therefore, it is particularly important to look for simple, high-sensitivity and high-specificity screening scale. With the advantage of simple operation and less time-consuming, clock drawing test (CDT) was proposed as early as the 1960s to assess a variety of cognitive function of patients. So far, there are more than 30 kinds of evaluation systems, while the effectiveness of each is not identical. This study is aimed to analyze the differences of performance between all kinds of error types in qualitative analysis of the CDT in terms of dementia subtypes and severity.Materials and methodsThe patients who had undertaken neuropsychological assessment at cognitive function testing room from January 2013 to October 2014 in Department of Neurology, Qilu Hospital of Shandong University, were screened and divided into four groups according to dementia subtypes and severity. The differences of performance of error types in qualitative analysis of the CDT between each group were compared. Qualitative analysis of the CDT was performed using a modified Rouleau CDT qualitative analysis, and the individual score and the total score were recorded. SPSS 21.0 was used to perform statistical analyses. The differences in age, education, MMSE score, CDT score between each group were compared through one-way ANOVA and post-hoc analysis. Chi-square test was used to analyze the differences in the probability of all kinds of error types of each group, and to further compare the distribution of every error type in mild, moderate and severe cases. ROC curves were constructed to look for the best cutoff value in the course of using qualitative analysis of the CDT to identify AD and VaD, and evaluate the sensitivity and specificity.Results74 patients were selected into "probable AD" group; 32 patients were selected into "probable VaD" group; 81 patients were selected into "other kinds of dementias(OD)" group; 66 subjects were selected into control group(Con group). There is no significant difference in age between each group. In the aspect of educational level, MMSE score and CDT score, Con group showed statistically significant differences with other three groups. The educational level of Con group was obviously higher than other three groups, while there is no difference between the three groups.Chi-square test showed that among four groups, six error types of qualitative analysis of the CDT except size and PER are of statistically significant difference. In the groups of mild, moderate and severe cases, which were divided on the basis of MMSE score, the incidence of the six categories of error in AD, VaD, OD groups and total distribution increased as the severity of disease increased. With the application of ROC curves, the best cutoff value for diagnosis of AD with qualitative analysis of the CDT was 15.5 points (AUC=0.821), and sensitivity and specificity were 70% and 82% respectively. The best cutoff value for the diagnosis of VaD was 16.5 points (AUC=0.837), and sensitivity and specificity were 55% and 97% respectively. Moreover, the best cutoff value for the diagnosis of cognitive impairment was 16.5 points (AUC=0.837), and sensitivity and specificity were 70% and 82% respectively.Conclusion(1) Qualitative analysis of the error types in CDT can be used to identify patients with various cognitive impairments. Graphic difficulties, conceptual deficits and spatial or planning deficits are the most common error types. This indicates that disorders of elaborate action controlling and planning, impairments of frontostriatal circuits and impairments of executive function exist in all kinds of dementias. Stimulus-bound response and perseveration have been found to be more common in AD than other kinds of dementias, which suggests that the injuries of prefrontal lobe are common seen in AD and lead to impairments of executive function and transformation disorders.(2) In the progression of dementia, the prevalence of all kinds of errors except perseveration increases significantly. In terms of dementia subtypes, stimulus-bound response in AD patients increases obviously as cognitive impairments progress besides the high incidence of conceptual deficits and spatial or planning deficits, which indicates frontal degeneration, temporo-parietal involvement and cortical and subcortical involvement occur in the course of disease-progression in AD. As for VaD patients, conceptual deficits are more common than graphic difficulties, indicating that their semantic memory-related function degrades fast and the probability of temporal involvement is high.(3) Qualitative analysis of CDT has high specificity in identifying cognitive impairment, but the sensitivity is low. Therefore, qualitative analysis of CDT is somewhat valuable in the diagnosis of cognitive impairment, but it can’t be used as a single method and needs to be combined with other scales to increase the sensitivity.