A comparison of clock and pentagon drawing in Alzheimer's disease

Abstract

Clock drawing is described as a novel, easily administered bedside measure of cognitive function. We examined from 77 ambulant elderly persons meeting NINCDS criteria for Alzheimer's disease their drawings of clock faces and overlapping pentagons. Interrater reliability for two previously published scoring scales for clocks and a devised ordinal scale for overlapping pentagons was high. There was moderate correlation with their total scores on the CAMCOG and Mini Mental State Exam (MMSE). However, a considerable number of patients scored within the normal range on all three drawing scales. A third (23/77) on clock drawing demonstrated their only abnormality at setting the time to 10 to 11 instead of the requested 10 past 11. For the clock drawing test to be used as a rapid screening instrument for Alzheimer's disease in the community an accurately drawn clock face must include the correct position of the hands. The pentagon test either alone or in combination did not enhance the accuracy of the clock test.