Psychometric properties of Clock Drawing Test and MMSE or Short Performance Test (SKT) in dementia screening in a memory clinic population.

Abstract

To evaluate five different scoring methods of the Clock Drawing Test (CDT) and to examine whether a combination of Mini Mental State Examination (MMSE) or Short Performance Test (Syndrom Kurz Test, SKT), respectively, with CDT can be used for cognitive screening. Retrospective blinded analysis of clock drawing performance using five scoring methods (Shulman et al. (1986), Sunderland et al. (1989), Wolf-Klein et al. (1989), Watson et al. (1997), Manos (1997)). A Memory Clinic at an academic psychiatric hospital (University of Frankfurt am Main, Germany). 123 consecutive patients (79 dementia patients, 44 controls). Inter-rater reliability and correlation of five different scoring methods of the CDT with established psychometric tests. Sensitivity and specificity of all five CDT's using the original and modified cut-off scores. Sensitivity, specificity and positive and negative predictive value of a combination of the CDT with MMSE and SKT, respectively. All scoring methods of the CDT showed a highly significant interrater reliability (0.82 to 0.94). Correlation with the MMSE and the SKT was also significant (p < 0.01) for all five CDTs. Highest sensitivity was achieved by the Shulman scoring method (81% sensitivity, specificity 79%). Sensitivity of all scoring methods could be improved up to 89% by modifying the originally proposed cut-off scores at the cost of lower specificity. By combining the CDT with the MMSE or the SKT, respectively, the sensitivity of each of the tests could be improved to 92% (SKT and Shulman scale). In patients with mild dementia (GDS 3), a combination of the Shulman Scale with the SKT (92%) and the MMSE (75%) achieved the highest sensitivity. The CDT in combination with the MMSE or SKT is an easily administered, non threatening and highly sensitive screening test for dementia in the setting of a memory clinic.