Clock drawing test in mild cognitive impairment: quantitative analysis of four scoring methods and qualitative analysis

Abstract

Background: The role of the clock drawing test (CDT) as a screening tool for dementia has been evaluated. However, studies focusing on mild cognitive impairment (MCI) are still lacking. The purpose of this study was to verify the validity of the CDT as a screening method for MCI.

Methods: 524 subjects aged 60 years and older were recruited in the community. Of these, 241 were diagnosed as not cognitively impaired (NCI) and 224 were classified as MCI. The CDT was scored according to the Freedman, Rouleau, Todd, and CERAD CDT and an additional comprehensive scoring system incorporating elements of most CDT for qualitative analysis.

Results: The sensitivity and specificity of the 4 CDT scoring systems for MCI ranged from 40.7 to 56.4% and from 71.8 to 85.3%, respectively. The likelihood ratio and the positive and negative predictive values of the 4 CDT ranged from 18 to 29, 18.2 to 24.5 and from 55.9 to 78.4%, respectively. In qualitative analysis, a significantly lower performance in the clock numbers category was observed in the MCI group.

Conclusion: This study suggests that although some qualitative analyses could help in identifying MCI individuals, the CDT is insufficient as a screening method to distinguish MCI individuals from NCI individuals in a clinical setting.