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Objective
Our aim was to specify the requirements of an architecture to serve as the foundation for standardized reporting of health information and to provide an exemplary application of this architecture.
Methods
The World Health Organization’s International Classification of Functioning, Disability and Health (ICF) served as the conceptual framework. Methods to establish content comparability were the ICF Linking Rules. The Rasch measurement model, as a special case of additive conjoint measurement, which satisfies the required criteria for fundamental measurement, allowed for the development of a common metric foundation for measurement unit conversion. Secondary analysis of data from the North Yorkshire Survey was used to illustrate these methods. Patients completed three instruments and the items were linked to the ICF. The Rasch measurement model was applied, first to each scale, and then to items across scales which were linked to a common domain.
Results
Based on the linking of items to the ICF, the majority of items were grouped into two domains, Mobility and Self-care. Analysis of the individual scales and of items linked to a common domain across scales satisfied the requirements of the Rasch measurement model. The measurement unit conversion between items from the three instruments linked to the Mobility and Self-care domains, respectively, was demonstrated.
Conclusions
The realization of an ICF-based architecture for information on patients’ functioning enables harmonization of health information while allowing clinicians and researchers to continue using their existing instruments. This architecture will facilitate access to comprehensive and consistently reported health information to serve as the foundation for informed decision-making.
Objective
Functioning is an important outcome in hand osteoarthritis (OA). The heterogeneity of patient‐reported outcome measures (PROMs) available challenges the direct comparability of information collected by these instruments. This study aimed to examine whether it is possible to achieve metric equivalence of PROMs commonly used to measure functioning in people with hand OA.
Methods
A secondary analysis of data from 253 persons who participated in the Vienna Hand Osteoarthritis Cohort Study was conducted applying the Rasch measurement model. Participants completed the Health Assessment Questionnaire, the Australian/Canadian Index for Hand Osteoarthritis, the Functional Index for Hand Osteoarthritis (FIHOA), and the Cochin Scale. The assumptions of stochastic ordering, local independence, unidimensionality, and invariance were tested for each scale independently before the scales were co‐calibrated onto a common metric.
Results
Except for the FIHOA, all measures indicated issues of local dependency in the initial analyses. After accommodating those with testlets, all scales satisfied the assumptions of the Rasch model (χ2 > 0.05). Marginal misfit in 2 items was found in the FIHOA, but this did not disturb person estimates. As the 4 scales form a common metric that satisfies the assumptions of the Rasch model, the scores can be equated.
Conclusion
The scores of the 4 hand function measures can be transformed to a common 0–100 metric, such that scores can be interchanged. A user‐friendly transformation table enables clinicians and researchers to have access to the common metric by simply adding up the total score for each instrument and identifying the corresponding transformed score on the common metric.
Metric properties of the Spinal Cord Independence Measure - Self Report in a community survey
(2016)
Objective: The Spinal Cord Independence Measure – Self Report (SCIM-SR) is a self-report instrument for assessing functional independence of persons with spinal cord injury. This study examined the internal construct validity and reliability of the SCIM-SR, when administered in a community survey, using the Rasch measurement model.
Methods: Rasch analysis of data from 1,549 individuals with spinal cord injury who completed the SCIM-SR.
Results: In the initial analysis no fit to the Rasch model was achieved. Items were grouped into testlets to accommodate the substantial local dependency. Due to the differential item functioning for lesion level and degree, spinal cord injury-specific sub-group analyses were conducted. Fit to the Rasch model was then achieved for individuals with tetraplegia and complete paraplegia, but not for those with incomplete paraplegia. Comparability of ability estimates across sub-groups was attained by anchoring all sub-groups on a testlet.
Conclusion: The SCIM-SR violates certain assumptions of the Rasch measurement model, as shown by the local dependency and differential item functioning. However, an intermediate solution to achieve fit in 3 out of 4 spinal cord injury sub-groups was found. For the time being, therefore, it advisable to use this approach to compute Rasch-transformed SCIM-SR scores.
Objective: Functioning is an important outcome to measure in cohort studies. Clear and operational outcomes are needed to judge the quality of a cohort study. This paper outlines guiding principles for reporting functioning in cohort studies and addresses some outstanding issues.
Design: Principles of how to standardize reporting of data from a cohort study on functioning, by deriving scores that are most useful for further statistical analysis and reporting, are outlined. The Swiss Spinal Cord Injury Cohort Study Community Survey serves as a case in point to provide a practical application of these principles.
Methods and Results: Development of reporting scores must be conceptually coherent and metrically sound. The International Classification of Functioning, Disability and Health (ICF) can serve as the frame of reference for this, with its categories serving as reference units for reporting. To derive a score for further statistical analysis and reporting, items measuring a single latent trait must be invariant across groups. The Rasch measurement model is well suited to test these assumptions.
Conclusion: Our approach is a valuable guide for researchers and clinicians, as it fosters comparability of data, strengthens the comprehensiveness of scope, and provides invariant, interval-scaled data for further statistical analyses of functioning.