Ann Rehabil Med.  2018 Apr;42(2):336-345. 10.5535/arm.2018.42.2.336.

Disability Measurement for Korean Community-Dwelling Adults With Stroke: Item-Level Psychometric Analysis of the Korean Longitudinal Study of Ageing

• Hong I
• Kim YJ
• Sonnenfeld ML
• Grattan E
• Reistetter TA

• KMID: 2432205
• DOI: http://doi.org/10.5535/arm.2018.42.2.336

Abstract

OBJECTIVE
To investigate the psychometric properties of the activities of daily living (ADL) instrument used in the analysis of Korean Longitudinal Study of Ageing (KLoSA) dataset.
METHODS
A retrospective study was carried out involving 2006 KLoSA records of community-dwelling adults diagnosed with stroke. The ADL instrument used for the analysis of KLoSA included 17 items, which were analyzed using Rasch modeling to develop a robust outcome measure. The unidimensionality of the ADL instrument was examined based on confirmatory factor analysis with a one-factor model. Item-level psychometric analysis of the ADL instrument included fit statistics, internal consistency, precision, and the item difficulty hierarchy.
RESULTS
The study sample included a total of 201 community-dwelling adults (1.5% of the Korean population with an age over 45 years; mean age=70.0 years, SD=9.7) having a history of stroke. The ADL instrument demonstrated unidimensional construct. Two misfit items, money management (mean square [MnSq]=1.56, standardized Z-statistics [ZSTD]=2.3) and phone use (MnSq=1.78, ZSTD=2.3) were removed from the analysis. The remaining 15 items demonstrated good item fit, high internal consistency (person reliability=0.91), and good precision (person strata=3.48). The instrument precisely estimated person measures within a wide range of theta (−4.75 logits <θ< 3.97 logits) and a reliability of 0.9, with a conceptual hierarchy of item difficulty.
CONCLUSION
The findings indicate that the 15 ADL items met Rasch expectations of unidimensionality and demonstrated good psychometric properties. It is proposed that the validated ADL instrument can be used as a primary outcome measure for assessing longitudinal disability trajectories in the Korean adult population and can be employed for comparative analysis of international disability across national aging studies.

Keyword

Stroke; Aging; Community survey; Reliability and validity; Outcome assessment

MeSH Terms

Activities of Daily Living
Adult*
Aging
Dataset
Humans
Longitudinal Studies*
Outcome Assessment (Health Care)
Psychometrics*
Reproducibility of Results
Retrospective Studies
Stroke*
Surveys and Questionnaires

Figure

• 

  Fig. 1 Standard error (SE) curve across the latent trait (θ). Dash line indicates the cut-off for SE which is equivalent to a reliability of 0.9. The activities of daily living instrument precisely estimated person measures located in a wide range of theta from −4.75 logits to 3.97 logits at a reliability level of 0.9.

• 

  Fig. 2 Person item-map. The numbers on the left side indicate the measures of person ability and item difficulty in logits. Each # on the left side of the map indicates three subjects and items are located on the right side of the map. The M to the left of the vertical line is the mean of the person measures and M to the right is the mean of the item difficulties. ‘Ss’ on the left and right of the vertical line indicates 1 standard deviation and the ‘Ts’ on the left and right of the vertical line indicates 2 standard deviations for item difficulty and person ability, respectively.

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