Scoring clock tests for dementia screening: a comparison of two scoring methods

OBJECTIVE: To compare the dementia screening performance of two scoring systems of the clock drawing test. METHODS: A sample of 1199 elderly subjects was administered the clock drawing test as part of a study on aging and dementia. The clock drawings were scored using published criteria for the two scoring systems that were compared. Additionally, a selection of 103 drawings was scored by three different raters to evaluate inter-rater agreement within each of the two methods. For a selection of 473 drawings the final diagnosis on the presence or absence of dementia was known. For these drawings accuracy for the detection of dementia was compared between the two methods. RESULTS: The four-item scoring system (Kappa 0.76; sensitivity 0.97; specificity 0.32; PPV 0.53; NPV 0.93) was found to be a little more reliable and as accurate as the six-item scoring system (Kappa 0.67; sensitivity 0.96; specificity 0.42; PPV 0.56; NPV 0.94). CONCLUSION: Since both scoring systems showed largely similar results, primary care physicians and other health care providers should be encouraged to use the four-item scoring checklist as it is easier and requires less time than the more elaborate checklist of the six-item system.