The Clock Drawing Test: A Valid Screening Instrument for Dementia Detection in Low-Educated Patients?

Objective: The non-verbal nature of the Clock Drawing Test (CDT) suggests it is a suitable cognitive screening instrument for populations with lower educational levels and/or language barriers. This study evaluates whether the CDT is a valid screening instrument for low-educated patients and includes a qualitative analysis of CDT errors. Method: A total of 503 participants were included, divided into four groups (dementia, MCI, no cognitive impairment, and other diagnosis), based on a clinical diagnosis by a geriatrician. Educational levels were categorized into four groups: no education and low, middle, and high education. CDT scores were assessed using the seven-point scoring system (Freedman), and two cutoff points were evaluated. Results: Results showed that in all education categories, the dementia group scored significantly lower on the CDT compared to the non-dementia group. The difference was smallest in participants with no education. Two cut-off points were assessed: <4 and <3. A cut-off of <4 showed better sensitivity versus <3, particularly for low-educated groups. A cut-off of <3 provided better specificity versus <4. Error analysis showed that errors made by low-educated participants without dementia were similar to those of patients with dementia. Conclusions: These findings show that the CDT (both total score and qualitative error analysis) has limited value in dementia case-finding in low-educated groups. The CDT is recommended primarily for middle- and high-educated groups.