Not throwing out the baby with the bathwater: lessons from the Fibromyalgia Impact Questionnaire.
The Fibromyalgia Impact Questionnaire (FIQ) is the most frequently used questionnaire in patients with fibromyalgia in the last 20 years. Recently, a revised version of the FIQ has been published. In this study, we examined the factor structure of the original version using explorative and confirmative factor analyses in a representative group of about 500 Dutch and Belgian patients with fibromyalgia, in which the work-related item was excluded. The FIQ consisting of a three-factor structure with a functional domain (ten items), physical symptom domain (six items), and mental symptom domain (two items), which is the most accurate. From the data presented, it is concluded that the FIQ is a solid, worldwide-used questionnaire with a history of 20 years consisting of three domains. When constructing a revised FIQ, the results of this study can be incorporated.