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Revised Italian version of FIQ showed reliability, validity for fibromyalgia patients
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The Italian Fibromyalgia Impact Questionnaire Revised version displayed reliability, internal validity and 2-D structure for patients with fibromyalgia, according to study results.
Researchers in Italy studied 503 patients with fibromyalgia (FM; mean age, 51.3 years; 423 women) with a mean symptom duration of 11.1 years. Patients completed the Italian Fibromyalgia Impact Questionnaire Revised version (FIQR), a 21-item updated version of the Fibromyalgia Impact Questionnaire, during clinical visits. The FIQR covered domains of function, symptoms and overall impact.
“The translation and cultural adaptation process of the Italian FIQR followed the published guidelines and no local adjustments were made except for a slight adaptation of item 13 related to ‘energy,’ ” the researchers said.
Rasch analysis (RA) was performed on the subscales of function (items 1-9) and symptoms (items 12-21), after factor analysis revealed their saliency. It was suggested through rating scale diagnostics that the 11 rating scale categories be consolidated to five.
After consolidation, RA showed that most items of the function and symptom subscales fit the respective constructs to measure (mean-square 0.7-1.3), with values between 0.8 and 1.2 indicating acceptability. The reliability levels of the two subscales were 0.88 and 0.83, respectively, for function and symptoms.
“To our knowledge, this is the first study investigating the dimensionality and validity of the FIQR using stringent criteria that included item response theory methods,” the researchers concluded. “Two of three domains were confirmed, whereas the third probably needs some more items in order to become an interpretable domain from a psychometric point of view.
“This preliminary study supports the usefulness of this questionnaire for measuring the multidimensional spectrum of FM-related functional and health-related quality of life problems, and provides a basis for further research aimed at improving its measurement qualities.”
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