The performance of the Clock Drawing Test in elderly medical inpatients: does it have utility in the identification of delirium?

The Clock Drawing Test is an often-used test for the detection of cognitive impairment, but the few studies that have evaluated its utility in delirium have produced rather inconsistent results. In a longitudinal study of delirium in elderly medical inpatients, we have investigated the relationships between the Clock Drawing Test, the presence and severity of delirium, and cognitive impairment. Using mixed linear model analysis we found that cognitive impairment was the major factor associated with low Clock Drawing Test scores (P < .0001): neither the presence nor the severity of delirium had additional significant effect on the Clock Drawing Test. Thus, we conclude that although the Clock Drawing Test is a good detector of cognitive impairment, it is not a suitable tool for detection of delirium in elderly medical inpatients.