Application of Clock Drawing Test in Evaluating Different Types of Dementias (Alzheimer’s Disease, Vascular Dementia and Fronto-temporal Dementia): A Cross-sectional Observational Study

Abstract

Introduction: The Clock Drawing Test (CDT) is a highly effective screening tool for assessing cognitive function. It complements the Mental State Examination (MSE) in the early detection of various types of dementia and the evaluation of cognitive functions. Documenting the specific type of error in clock drawing significantly enhances the clinical evaluation of dementia patients in an economical manner. The CDT can effectively detect errors in execution and visuospatial functions associated with different types of dementia, including Alzheimer’s Disease (AD), Vascular Dementia (VD), and Frontotemporal Dementia (FTD). Additionally, it allows for a comparative analysis of the CDT with the severity of dementia assessed by the Bengal Mental Status Examination (BMSE) Scale. Aim: Present study aims to determine the ability of the CDT to scriminate these three disorders AD, VD, and FTD by analysing patterns of error in clock drawing. Materials and Methods: This cross-sectional observational study was conducted at the Department of Neuromedicine, Memory Clinic, Medical College, Kolkata, West Bengal, India, from March 2019 to February 2020. The diagnosis of dementia was made based on the Diagnostic and Statistical Manual of Mental Disorders- Fifth Edition (DSM-V) criteria for AD and VD, and the Rascovsky Criteria for FTD. A total of 80 patients were included in the study, with 40 in the AD group, 30 in the VD group, and 10 in the FTD group, considering 80% power and a 5% probability of error. Dementia severity was assessed using the BMSE [Annexure-III]. The subjects were provided with an 8.5×11-inch blank sheet of paper and a pencil, and were asked to draw a clock, including all the numbers, and set the hands to 10 minutes past 11. They were also requested to copy a clock as accurately as possible from a model. The resulting drawings were then analysed quantitatively by revised scale score and qualitatively using Rouleau’s qualitative analysis of clock drawing. Numerical variables were compared between groups using the Analysis of Variance (ANOVA) test and the Wilcoxon test, depending on the distribution’s normalcy. All analyses were two-tailed, and p<0.05 was considered statistically significant. Results: When comparing the revised quantitative scale, the CDT score showed a significant difference between the three groups (AD, VD, and FTD) with mean scores of 2.91, 2.9, and 0.7, respectively (p=0.01). The size of the drawn clocks also showed a significant difference (p=0.006) among the AD, VD, and FTD groups, with sizes of 21.27, 18.63, and 16.7, respectively. The BMSE score also showed a significant difference between AD and FTD (p<0.05), as well as between AD and VD (p<0.05). Clock size was significantly different between AD and VD (p<0.05). There were no significant differences observed regarding graphical difficulty, stimulus-bound response, conceptual deficits, spatial and/or planning deficits, and perseveration among the three groups. Conclusion: Qualitative analysis of the CDT contributes to the identification of different types of dementia by enabling the description of specific errors. A significant inter-group difference was found in the BMSE score, but it could not pinpoint the domains of cognitive deficits, whereas the CDT can detect those.