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Paper text:
cognitive impairment caused by various diseases associated with the aging of the population 
 has become a recent concern1 .
although many studies have been done on 
 patients with cognitive disorders , a clinical screening tool for specific cognitive 
 characteristics has not been developed3 .
stroke patients show cognitive disorders during the neurological recovery process , making 
 early intervention through screening necessary4 .
the mini - mental state evaluation ( mmse ) , which is commonly used for 
 screening cognitive impairment , has been studied in patients with dementia5 .
simple methods of screening for stroke 
 patients with cognitive characteristics and objective inspection tools are needed .
the clock drawing test ( cdt ) developed by applying rasch analysis can screen patients with 
 cognitive impairment in a short time . the appropriate items and rating scales for the cdt 
 were selected according to the characteristics of cognitive problems in a previous 
 study6 . on the other hand ,
therefore , the aim of this 
 study was to confirm the clinical usefulness of the cdt by applying rasch analysis to 
 predict cognitive impairment .
the study participants were enrolled 
 from patients at 10 rehabilitation hospitals in south korea . all subjects provided written 
 informed consent to participate in this study in accordance with the ethical standards of 
 the declaration of helsinki .
participants without visual problems or a history of other 
 neurological diseases other than stroke were included .
the mmse is the most widely used assessment tool for the screening of cognitive 
 abilities7 . in this study , 187 patients 
 were evaluated by the cdt developed through rasch analysis along with the mmse .
the data were analyzed 
 according to the general characteristics of the subjects to increase the clinical utility of 
 the cdt .
in addition , the cutoff point was classified to identify cognitive impairment in 
 the cdt , and the sensitivity and specificity were analyzed .
the cdt composed of 16 items in 
 6 areas could objectively evaluate the cognitive characteristics based on the task to be 
 carried out6 .
analysis of variance was performed to examine the significance of the mmse and cdt 
 according to the general characteristics of the subjects .
receiver operating characteristic 
 ( roc ) analysis was performed to produce a cutoff point for cognitive impairment and 
 calculate the sensitivity and specificity values .
roc analysis was used to determine the 
 optimal cutoff values and the cognitive dysfunction of bias in this study .
a comparison of the mmse and cdt in accordance with the general characteristics of the 
 subjects showed significant differences according to gender , age and education for both 
 tools ( table 1table 1.difference between the mmse and cdt according to general characteristics of the 
 participants ( n=182)characteristicsnmmsepost hoccdtpost hoc(m  sd)(m  sd)gendermale11723.2  5.9(a >
b)10.6  3.8(a > b)female6521.5  5.38.7  4.0age 49 or less2325.0  5.5(a , b , d > e)12.1  2.9(a , b > e)(years)50594424.6  3.911.3  3.2(a >
d)60695321.5  6.79.5  4.370794522.6  5.19.1  3.780 or more1717.6  5.46.8  3.8educationno education1521.9
 4.1(d , e > b)6.4  3.7(d , e > a , b)(school)elementary5520.3  6.28.7  3.9middle1823.0
 3.99.2  3.5high4723.8  5.511.0  3.6university or more4724.1  5.911.5  3.4after stroke3 or less5621.8  5.59.1  4.3(months)462522.3  6.09.6  4.27122523.0  5.210.4  3.813243725.1  3.410.9  3.225 or more3921.3  7.410.0  3.9dominant handright17322.6  5.79.8  3.9left421.5  8.39.5  5.5both524.4  6.012.2  3.6affected
side(brain)right9323.1  5.410.1  3.9(a , b > c)left8022.3  6.110.0  3.9both , etc.920.2  7.36.7  3.8type of damageinfarction13422.7  5.79.9  4.0hemorrhage4722.6  6.19.9  3.9other116.0 
0.08.0  0.0item number in areas ( a=1 , b=2 , c=3 , d=4 , e=5 ) ) . in both tools , males showed higher cognitive skills than women . in the case 
 of age , those 7080 years of ages showed significant differences compared with younger 
 patients . in the case of education , patients with no education or an elementary school 
 education showed significant differences compared with those with a high school or college 
 education .
analysis of the duration after stroke revealed a significant difference between 
 the tools , but there were no significant differences according to time period .
item number in areas ( a=1 , b=2 , c=3 , d=4 , e=5 ) a total cdt score of 10.5 , which was selected as the cutoff point to identify cognitive 
 impairment , showed sensitivity , specificity , and youden index values of 86.4% , 91.5% , and 
 0.8 .
in addition , the cdt showed positive and negative predictive values of 95% and 88.2% , 
 respectively , compaired with the mmse ( table 
 2table 2.prediction of cognitive impairment in accordance with the cdt ( n=182)cdt ( total score)mmse ( total score)predictive value ( % ) cognitive impairment ( < 24)normal ( 24)10764ppv=95.0>111290npv=88.2youden index ( % ) sensitivity=86.4 , specificity=95.7ppv : positive predictive value ; npv : negative predictive value ) .
this study was performed to enhance the clinical usefulness of the cdt by applying rasch 
 analysis for predicting of cognitive impairment .
the cdt can enable the assessment and early 
 intervention in patients with cognitive impairment8 .
the usefulness of cdt for the screening of cognitive impairment has been reported . in 
 particular
, the cdt applying rasch analysis is an objective and reliable assessment tool , 
 and it enables the ability of individuals can be evaluated mathematically9 , 10 . 

examination of the validiry of the cdt by comparison with the mmse showed similar 
 significant differences according to gender , age , and education .
the cdt and mmse reflect 
 different cognitive characteristics , which may have affected the results .
these results 
 showed that the cdt could be a useful tool for the screening of cognitive impairment5 , 11 .
rasch analysis was applied to the cdt for tool development because it enables the ability 
 of individuals be measured accurately by based on the item response theory .
the clinical 
 advantage of the cdt in screening for cognitive disorders was confirmed through roc 
 analysis12 .
the standard cdt determines 
 that a patient may have a cognitive impairment when the patient scores have less than 10 
 points .
the positive predicted value was 95.0% , which represents the probability of 
 cognitive dysfunction for positive test results , and the negative predictive value was 
 88.2% , which represents the probability of cognitive function being normal for negative test 
 results ; these values were based on a cutoff of 10 points .
the cdt is believed to be useful 
 in assessments and interventions based on its excellent ability to identify cognitive 
 impairment6 , 13,14,15 .
in addition , it must not be 
 sensitive to different environments , and the sensitivity and specificity must be high16 .
therefore , the cdt applying rasch 
 analysis is a useful tool for screening high - risk patients with cognitive impairment . 
 nevertheless , a follow - up study of the cdt for patients with a variety of diseases will be 
 needed .
[ purpose ] this study examined the clinical usefulness of the clock drawing test applying 
 rasch analysis for predicting the level of cognitive impairment . [ subjects and methods ] a 
 total of 187 stroke patients with cognitive impairment were enrolled in this study . 
 the 
 187 patients were evaluated by the clock drawing test developed through rasch analysis 
 along with the mini - mental state examination of cognitive evaluation tool . 
 an analysis of 
 the variance was performed to examine the significance of the mini - mental state 
 examination and the clock drawing test according to the general characteristics of the 
 subjects . 
 receiver operating characteristic analysis was performed to determine the cutoff 
 point for cognitive impairment and to calculate the sensitivity and specificity values . 
 
 [ results ] the results of comparison of the clock drawing test with the mini - mental state 
 showed significant differences in according to gender , age , education , and affected side . 
 
 a total cdt of 10.5 , which was selected as the cutoff point to identify cognitive 
 impairement , showed a sensitivity , specificity , youden index , positive predictive , and 
 negative predicive values of 86.4% , 91.5% , 0.8 , 95% , and 88.2% . 
 [ conclusion ] the clock 
 drawing test is believed to be useful in assessments and interventions based on its 
 excellent ability to identify cognitive disorders .