Psychometric Properties of the Persian Version of the Clock Drawing Test (CDT) Among the Aged People in Iran

The population of old people in Iran is increasing, as well as the prevalence of dementia. For early detection and intervention, proper dementia screening tools are needed. The clock drawing test (CDT) is a quick, inexpensive and well accepted test for the screening of cognitive problems. The aim of this study was to evaluate psychometric properties of CDT among aged people in Iran. The clock drawing test, using Shulman’s modified scoring method, was performed on 74 aged members of Iran’s Alzheimer Association services in Tehran from May to September 2012 convenient sampling method was used. The participants with the following characteristics were selected: age 60 years or more, able to communicate and with 4 years of formal education. Using the diagnostic criteria for dementia of the diagnostic and statistical manual of mental disorder, 4th edition, (DSM-IV) as a gold standard, the difference between CDT mean scores of dementia and non-dementia patients were evaluated. The receiver operating characteristics (ROC) curve was used to determine the optimal cut off points for CDT using the 20th version of SPSS. The mean age of participants was 72 ± 7.95 years. There was a significant difference between the scores of participants with and without dementia (P < 0.001). The best cut off point was 3/4 with 90% sensitivity and 73% specificity. The area under the ROC curve was 0.896 (P < 0.001), which indicates proper accuracy of the test. The clock drawing test has acceptable psychometric properties among the aged people of Iran. The Persian version of CDT can be applied for the screening and monitoring cognitive problems in this population. Further studies are required to assess the impact of literacy level and different scoring systems on the accuracy of the results obtained by the CDT.