Measuring health in patients with fibromyalgia: content comparison of questionnaires based on the International Classification of Functioning, Disability and Health.

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.