Validation of a Persian version of the Fibromyalgia Impact Questionnaire (FIQ-P)

The aim of this study is to translate, adapt, and validate a Persian version of the Fibromyalgia (FM) Impact Questionnaire (FIQ-P). The FIQ-P was adapted following the translation and back-translation approach; then, it was administered to thirty females with FM. Participants also completed two other validated questionnaires, the Medical Outcome Survey Short Form-36 (SF-36) and the Beck Depression Inventory (BDI). Internal consistency within the FIQ-P items and its test-retest reliability were assessed with Cronbach's alpha and Spearman's correlation coefficient, respectively. Construct validity was analyzed by Spearman's r when correlating the FIQ-P to other questionnaires. The translated version was concordant. Adaptation affected two sub-items of physical function. Participants' mean age ± standard deviation was 40.4 ± 9.0 years. Internal consistency proved good with α = 0.80. Test-retest coefficient ranged from 0.50 for the item "work days missed" to 0.79 for all FIQ-P items. Fair and statistically significant (P < 0.01) correlations were found between the FIQ-P items and two other questionnaires, SF-36 (r = -0.57) and BDI (r = 0.53). We concluded that the FIQ-P is a valid and reliable instrument for measuring health status of Persian-speaking FM patients.