Participation and social functioning in patients with fibromyalgia: development and testing of a new questionnaire.

Background: While there are numerous instruments for capturing the symptoms of fibromyalgia syndrome (FMS) patients, there is a lack of questionnaires capable of measuring in detail FMS patients' participation and social functioning. It was our aim to develop and methodologically test a new patient questionnaire specific to FMS measuring these concepts (the "Fibromyalgia Participation Questionnaire" FPQ).

Methods: We first conducted a qualitative prestudy (focus groups, N = 38) to identify which impairments FMS patients experience in daily life because of their illness. To analyze the data we developed a coding system that contained 10 supercategories and a total of 105 subcategories. Items for the FPQ were developed from the subcategories. The psychometric analysis was done on a sample of N = 256 FMS patients undergoing inpatient rehabilitation in Germany.

Results: The final version of the FPQ contained 27 items and three scales (participation in social life FPQ-S, 11 items; participation in daily life FPQ-D, 11 items, participation in work-life FPQ-W 5 items). The FPQ displays good distribution properties, all the scales are unidimensional, and the scales fit to the Rasch model. Cronbach's Alpha range from 0.85 to 0.94. We noted indications of construct validity in that the FPQ correlates as expected with the Fibromyalgia Impact Questionnaire (physical scale), Pain Disability Index and scales from the PROMIS® item banks for satisfaction with participation. The FPQ scales generally reveal greater responsiveness than other instruments. By linking FPQ items to the categories of the International Classification of Functioning, Disability and Health (ICF) we demonstrate content validity.

Conclusions: The FPQ captures participation and social functioning in FMS patients. As its psychometric properties are good, it can be recommended for use in evaluation studies and clinical trials.