Correlation between the CAMCOG, the MMSE, and three clock drawing tests in a specialized outpatient psychogeriatric service

Our objective was to assess the correlation between (1) the Cambridge Cognitive Examination (CAMCOG) (including the Mini-Mental State Examination [MMSE]) score and three clock drawing tests (CDT) and (2) the three CDTs independently, in a specialized outpatient psychogeriatric service. One hundred and fourteen subjects completed a comprehensive evaluation and were allocated to one of the following groups: dementia of the Alzheimer's type (DAT) in 52; vascular dementia (VD) in 36; non-dementia (ND; Mood or Anxiety Disorders) in 26. When the entire sample of patients is considered, all three CDTs used were highly and significantly correlated to the MMSE score, the CAMCOG score, and to each other. In this patient population, these cognitive tests may be interchangeable for providing an initial objective measure of cognitive function. However, when the same correlations were studied in the separate diagnostic groups, in the dementia group (DAT and VD) even though the high correlations between the various CDTs themselves did not change, the correlations between the MMSE score, the CAMCOG score and the CDTs decreased, more evidently in the VD group. This trend became even more conspicuous in the ND group, where some of the above mentioned correlations became non-significant. We hypothesize that in a real clinical situation the clinician initially assumes the role of cognitive "evaluator" (in terms of the total sample) followed by the role of cognitive "monitor" (in relation to specific diagnostic groups). In the first instance, CDTs, the MMSE, and the CAMCOG might be considered interchangeable as an initial objective measure of cognitive dysfunction, while in the second role, different CDTs might be diversely used, presumably supplemented by other cognitive tests and clinical methods.