Psychometric properties and validation of the polish version of the Fibromyalgia Impact Questionnaire (FIQ-Pol)

Abstract Background Fibromyalgia (FM) is a chronic condition characterized by widespread musculoskeletal pain, fatigue, intestinal disorders, mood swings, and sleep disturbances. To the best of our knowledge, the questionnaire used for assessing problems and difficulties in the functioning of people with FM has not been translated and adapted in Poland so far. The aim of the study was to assess the psychometric properties of the Polish version of the Fibromyalgia Impact Questionnaire (FIQ-Pol). Material and method The study covered 150 people with FM living in Poland. The measurement reliability, internal structure, repeatability, and validity of the Polish version of the FIQ were examined. Results The scale score reliability of the entire tool for the research group was very good. The alpha Cronbach's test result for the whole scale was 0.84. The repeatability of the scale measured by the test–retest method using the interclass correlation coefficients (ICC) was very good and amounted to 0.96. Internal structure suggested by FIQ-Pol authors was confirmed (Confirmatory factor analysis). After introducing modification indices for the entire scale, satisfactory parameter values were obtained, i.e.: RMSEA (0.06), CFI (0.97) and TLI (0.96). Theoretical validity was assessed by correlating the results of the Polish version of the FIQ with the results of the Beck's Depression Inventory (BDI). Both the FIQ-Pol total score and its domains showed strong positive correlations with BDI. Conclusion The Polish FIQ is a reliable and valid tool to measure the functional disability and health status of Polish people with FM.