Open Access

Objective To analyze the content of outcome measures commonly used to assess health in patients with fibromyalgia (FM) by linking the items of the instruments with the International Classification of Functioning, Disability and Health (ICF) in order to evaluate the adequacy of currently used measures. Methods Questionnaires used in FM were identified in a structured literature search. All concepts included in the items of the questionnaires were linked to ICF categories, according to previously published linking rules, by 2 independent health professionals. The percentages of linked ICF categories addressing the different ICF components were calculated. Results Generic and symptom‐specific instruments were included. From the 296 items contained in all 16 instruments, 447 concepts were extracted and then linked to 52 ICF categories of the component body functions, 1 category of the component body structure, 40 categories of the component activities and participation, and 9 categories of the component environmental factors. More than half of the concepts identified were linked to body function, fewer were linked to activities and participation, and only concepts of 4 instruments were linked to the ICF component environmental factors. Conclusion Many concepts were linked to the categories in the ICF component body functions. While linking to the broad category, purportedly similar instruments often covered widely varying areas of function at more fine‐grained levels of detail. Some categories, such as environmental factors, were barely covered by any of the instruments and might constitute an important aspect of health deserving better coverage and future development.

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.

Objectives: Instruments to assess functioning in patients with FM vary considerably in their content and are often symptom‐specific. This study aimed to examine whether it is feasible to construct a psychometric‐sound clinical instrument to measure functioning in FM based on the Brief ICF‐Core‐Set for chronic widespread pain (CWP). Methods: Two hundred and fifty six people with FM completed the Brief ICF‐Core‐Set. The Rasch model was used for analysis. Once ordering of response options of ICF categories was ensured, the following properties were studied: fit of the ICF categories to the Rasch model, the targeting between ICF categories and a person’s abilities, unidimensionality, and reliability. Results: Six ICF categories were rescored due to disordered thresholds. Five ICF categories were removed due to high model‐misfit and differential item functioning (DIF) for gender. Scores from 46 participants were excluded due to extreme scores. The ICF categories included display consistency with an underlying unidimensional construct, are free of DIF for age, disease duration and gender, display excellent overall reliability, and cover a range of functioning difficulties. Conclusions: This study illustrates that it is possible to measure functioning as a unidimensional construct based on selected ICF categories from the components body functions, as well as activities and participation of the Brief ICF‐Core‐Set for CWP in patients with FM.

Purpose The content of and methods for collecting health information often vary across settings and challenge the comparability of health information across time, individuals or populations. The International Classification of Functioning, Disability and Health (ICF) contains an exhaustive set of categories of information which constitutes a unified and consistent language of human functioning suitable as a reference for comparing health information. Methods and results In two earlier papers, we have proposed rules for linking existing health information to the ICF. Further refinements to these existing ICF Linking Rules are presented in this paper to enhance the transparency of the linking process. The refinements involve preparing information for linking, perspectives from which information is collected and the categorization of response options. Issues regarding the linking of information not covered or unspecified within the ICF are also revisited in this paper. Conclusion: The ICF Linking Rules are valuable for enhancing comparability of health information to ensure that information is available in a consistent manner to serve as a foundation for evidence-based decision-making across all levels of health systems. The refinements presented in this paper enhance transparency in, and ultimately reliability of the process of, linking health information to the ICF. Implications for Rehabilitation The International Classification of Functioning, Disability and Health (ICF) constitutes a unified and consistent language of human functioning suitable as a reference for comparing health information. Comparability of information is essential to ensure that the widest range of information is available in a consistent manner for any decision-maker at all levels of the health system. The refined ICF Linking Rules presented in this article outline the method to establish comparability of health information based on the ICF.