We aimed to evaluate the psychometric properties of the IADL measure included in the Dementia Care Assessment Packet (DCAP-IADL) in dementia patients.
The study involved 112 dementia patients and 546 controls. The DCAP-IADL was scored in two ways: observed score (OS) and predicted score (PS). The reliability of the DCAP-IADL was evaluated by testing its internal consistency, inter-rater reliability and test-retest reliability. Discriminant validity was evaluated by comparing the mean OS and PS between dementia patients and controls by ANCOVA. Pearson or Spearman correlation analysis was performed with other instruments to assess concurrent validity. Receiver operating characteristics curve analysis was performed to examine diagnostic accuracy.
Chronbach's α coefficients of the DCAP-IADL were above 0.7. The values in dementia patients were much higher (OS=0.917, PS=0.927), indicating excellent degrees of internal consistency. Inter-rater reliabilities and test-retest reliabilities were statistically significant (p<0.05). PS exhibited higher reliabilities than OS. The mean OS and PS of dementia patients were significantly higher than those of the non-demented group after controlling for age, sex and education level. The DCAP-IADL was significantly correlated with other IADL instruments and MMSE-KC (p<0.001). Areas under the curves of the DCAP-IADL were above 0.9.
The DCAP-IADL is a reliable and valid instrument for evaluating instrumental ability of daily living for the elderly, and may also be useful for screening dementia. Moreover, administering PS may enable the DCAP-IADL to overcome the differences in gender, culture and life style that hinders accurate evaluation of the elderly in previous IADL instruments.
The decline of functional activities is the critical feature in the diagnosis of dementia.
ADL can be divided into basic ADL (BADL) and instrumental ADL (IADL). BADL include self-maintenance skills such as bathing, dressing and toileting. IADL refers to daily activities that are not necessary for fundamental functioning, but enable the individual to live independently within a community (light housework, preparing meals, taking medications, shopping, using the telephone, managing money and so on).
IADL can be measured in three ways: self-reported questionnaires, performance-based assessment and informantbased questionnaires.
Despite the widespread use of these assessment tools, there are some limitations in the current measures of IADL. First, some measures include items that are relatively unrelated to IADL (memory, comprehension, or social functioning).
To overcome these limitations in the currently available IADL measures, the IADL measure included in the Dementia Care Assessment Packet (DCAP-IADL)
The participants consisted of 112 dementia patients (79 Alzheimer's disease, 25 vascular dementia, 1 frontotemporal dementia, 4 dementia of Lewy body disease, 4 Parkinson's disease dementia, and 3 other dementia) and 546 non-demented elderly controls aged 60 years or older. The non-demented elderly subjects were community-dwelling Korean elders who participated in the Korean Longitudinal Study for Health and Aging (KLoSHA).
The demographic characteristics of the subjects are presented in
The DCAP-IADL consists of a total of 10 items that include 3 community items (mode of transportation, going outside within walking distance, and shopping), 5 personal management items (ability to use the telephone, ability to use electric appliances, ability to handle money, ability to manage personal belongings, and being responsible for own medication), and, 2 household items (housekeeping and food preparation). "Laundry", although it is an important and common activity of daily living, is not included since it is barely performed by men in Asian cultures. All items are rated based on observations in the recent 90 days. Each item is rated from 0 to 3 points. The total score of the DCAP-IADL is 30 points, and a higher score indicates lower instrumental activities of daily living. We scored the DCAP-IADL in two ways: observed score (OS) and predicted score (PS). For scoring OS, informants were asked to score each item based on observations in the recent 90 days. If an item could not be observed during this time period, it was scored as 3 points, which is equivalent to "cannot be carried out". However, in scoring PS, informants were asked to give their best guesses on the items that they have not experienced instead of giving 3 points. For instance, if a female subject did not manage financial matters because her husband takes exclusive charge of handling finance, we requested her informant to predict whether she would be able to manage financial matters if her husband did not take on the job.
Three aspects of reliability were examined internal consistency of scale, inter-rater reliability and test-retest reliability. Internal consistency was examined by Crohnbach's alpha. In order to evaluate inter-rater reliability, 36 dementia patients and 8 non-dementia controls were rated with the DCAP-IADL simultaneously by two independent researchers (tester and rater). The DCAP-IADL was administered again to 17 dementia patients and 13 non-dementia controls by the same rater at 2-4 weeks after the initial assessment. For evaluating inter-rater and test-retest reliabilities, Pearson correlation coefficients were calculated.
To evaluate discriminant validity, the mean OS and PS were compared between the dementia patients and non-demented subjects by ANCOVA after adjusting for age, sex and educational level. We evaluated the concurrent validity of the DCAP-IADL by calculating its Pearson correlation coefficients with K-IADL,
To examine diagnostic accuracy, we performed receiver operating characteristics (ROC) curve analysis for both OS and PS of the DCAP-IADL and compared their areas under the ROC curves (AUC) with those of K-IADL and MMSE-KC.
All statistical analyses were performed using SPSS for windows, version 13.0 and Medcalc for windows, version 12.2.1.0 (MedCalc Software, Mariakerke, Belgium).
The results of the reliability analysis are presented in
As shown in
In the present study, the DCAP-IADL was found to be a reliable and valid instrument for evaluating functional abilities of the elderly. A noteworthy result was that the reliability and validity of PS were comparable to or slightly better than those of OS. Most informant-based IADL instruments include some items that are not equally applicable to both genders in some cultures or not applicable in certain life styles. For example, in general, men do not prepare meals and women do not handle finances in many Asian cultures. Elders who lived with their children or dwell in nursing homes may not perform housekeeping duties, laundry, and food preparation by themselves. These items that subjects do not normally experience were not rated or given a minimum score in most previous IADL instruments. However, the DCAP-IADL excluded or minimized items that could be influenced by gender, culture, dwelling environment and life style. Moreover, to evaluate items that subjects have not experienced within an observation window, we used PS simultaneously with OS instead of excluding that item from the overall score or giving it a minimum score. In the PS of the DCAP-IADL, we asked informants to make their best guesses for the IADL items that could not be directly observed. Pre-existing tools did not adopt the scoring system like PS due to the concern of informant bias. However, our results suggest that the discriminant and concurrent validity of PS were comparable to or slightly better than those of OS. As
In conclusion, the DCAP-IADL is a reliable and valid instrument for evaluating the instrumental ability of daily living for the elderly, and may also be useful for screening dementia. Moreover, administering PS may enable the DCAP-IADL to overcome the differences in gender, culture and life style that hinder accurate evaluation in previous IADL instruments.
This study was supported by a grant from the Korean Health Technology R&D Project, Ministry for Health, Welfare, & Family Affairs, Republic of Korea (Grant No. A092077) and by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MEST; Grant No. 2011-0018262). Also, this study was supported by an independent research grant from AstraZeneca Pharmaceuticals (Grant No. RC200811-399). The sponsors had no role in shaping the design, conduct, interpretation or summary of this research.
Mean scores on the Dementia Care Assessment Packet Instrumental Activities of Daily Living (DCAP-IADL) for the 3 different dementia stages according to CDR severity indices. All mean scores of the observed score and predicted score of DCAP-IADL differed significantly from one another by post hoc analysis (Bonferroni comparison, p<0.05). *p=0.013 by paired t-test, **p=0.001 by paired t-test. CDR: Clinical Dementia Rating scale.
The area under curve (AUC) of DCAP-IADL observed score, DCAP-IADL predicted score, K-IADL, and MMSE-KC. DCAP-IADL: the Dementia Care Assessment Packet Instrumental Activities of Daily Living, K-IADL: Korean Instrumental Activities of Daily Living, MMSE-KC: the Korean MMSE version of the Consortium to Establish a Registry for Alzheimer's disease, ROC: Receiver Operating Characteristics.
Demographic characteristics of non-demented control subjects and dementia patients
Number (percent) of subjects unless otherwise indicated. CDR: Clinical Dementia Rating Scale
Results of reliability test for non-demented control subjects and dementia patients
*all correlations are significant at 0.05 level by Pearson correlation analysis. IC: internal consistency, IR: inter-rater reliability, TR: test-retest reliability, DCAP-IADL: the Dementia Care Assessment Packet-Instrumental Activities of Daily Living
Mean scores of DCAP-IADL, K-IALD, BDS-ADL, and MMSE-KC in non-demented control subjects and dementia patients
*mean scores of dementia patients are significantly different from non-dementia subjects after controlling for age, sex and education level by ANCOVA. DCAP-IADL: Dementia Care Assessment Packet-Instrumental Activities of Daily Living, K-IADL: Korean Instrumental Activities of Daily Living, BDS-ADL: Blessed Dementia Scale-Activities of Daily Living, ANCOVA: analysis of covariance, MMSE-KC: the Korean MMSE version of the Consortium to Establish a Registry for Alzheimer's Disease
Correlation between the Dementia Care Assessment Packet Instrumental Activities of Daily Living (DCAP-IADL) and other instruments for evaluating activities of daily living, global cognition and global severity of dementia
All correlations are significant at p<0.01, by Pearson correlation (K-IADL, BDS-ADL, MMSE-KC, and CDR-SOB) and Spearman correlation analysis (CDR). K-IADL: Korean Instrumental Activities of Daily Living, BDS-ADL: Blessed Dementia Scale-Activities of Daily Living, MMSE-KC: the Korean MMSE version of the Consortium to Establish a Registry for Alzheimer's Disease, CDR: Clinical Dementia Rating scale, CDR-SOB: Clinical Dementia Rating scale-Sum of Box
Sensitivity and specificity of the Dementia Care Assessment Packet Instrumental Activities of Daily Living (DCAP-IADL) for diagnosis of dementia patients
*optimal cut-off point as determined by ROC analysis. AUC: Area Under Curve, ROC: Receiver Operating Characteristics