The Mini-Cog, Clock Drawing Test, and the Mini-Mental State Examination in a German memory clinic: specificity of separation dementia from depression.

BACKGROUND: The aim of this study was to assess the specificities of the Mini-Cog, the Clock Drawing Test (CDT), and the Mini-Mental State Examination (MMSE) against depression and healthy controls in a German Memory Clinic. Furthermore, we analyzed the specificities of all three screening instruments in dependence of actual depression severity.
METHODS: Data from 142 depressed elderly, 438 dementia patients, and 64 healthy controls were retrospectively analyzed. The CDT and an extraction of the three-item recall of the MMSE were used to constitute the Mini-Cog algorithm. Depression severity was rated by either the Beck Depression Inventory (BDI) or the Geriatric Depression Scale (GDS) depending on the age of the patients.
RESULTS: The Mini-Cog achieved a specificity of 79.6% against depressed elderly and 100.0% against healthy subjects (p < 0.001). Similarly, the specificities of the CDT (83.8%) and MMSE (92.3% at a cut-off ≤24 and 90.8% at ≤25, respectively) against healthy subjects were significantly higher than the specificities against depressed patients (each p < 0.05). Concerning the depressed patients, the MMSE demonstrated significant higher specificity than the Mini-Cog and the CDT, but also showed the lowest sensitivity for the detection of dementia. Surprisingly, the depression severity had no effect on the specificity of the Mini-Cog and the CDT, only the MMSE was susceptible for the depression severity.
CONCLUSION: Although the MMSE showed higher specificities, the weighting between the sensitivities and specificities in all tests prove again the Mini-Cog as a short, valid, and sensitive screening tool.