Construction Tasks in Diagnosis of Early Cognitive Impairment - A Critical Revisitation

This study aimed to look at the utility of the clock drawing test (CDT) and cube construction test (CCT) in diagnosing early cognitive impairment (ECI) and the correlations among various demographic variables and neuropsychological tests.

This is a retrospective study with data collected from an ongoing registry. Elderly with at least 8 years of formal education were categorized into cognitively normal (CN), mild cognitive impairment (MCI), and early dementia (ED) as per established criteria. Their CDT and CCT scores were assessed using a scoring system and errors were also analysed by the principal investigator blinded to the clinical diagnosis.

A total of 228 subjects with a mean age of 69 ± 6.7 years were categorized into three groups: 80 CN subjects, 77 with MCI, and 71 with ED. Age was negatively and the level of education was positively correlated to CDT and CCT scores among CN, but not in ECI. Qualitative errors on CDT included significantly more graphic, spatial, and conceptual errors and stimulus-bound responses among ED compared to CN and the latter two error subsets compared to MCI. Logistic regression revealed that higher age and lower quantitative CDT scores were independent predictors for classifying ECI from CN. The addition of qualitative errors of CDT rendered a greater effect size in classifying ED from MCI and CN.

CDT and CCT scores performed better in diagnosing ED and MCI from CN. CDT scored better as a diagnostic tool than CCT possibly due to better objectivity in the scoring system with qualitative information.