Psychometric properties of Polish version of the 36-item WHODAS 2.0 in individuals with fibromyalgia

Fibromyalgia (FM) is chronic, widespread musculoskeletal pain and accompanying fatigue, sleep disturbances, cognitive, psychological, and somatic symptoms. The aim of the study is to assess the psychometric properties of the Polish version of the 36-item WHODAS 2.0 in FM patients. This is a cross-sectional study involving 456 FM polish patients. The World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) 36-item version, the Fibromyalgia Impact Questionnaire (FIQ) and Beck's Depression Inventory (BDI) were used as an assessment tool in the study. The internal consistency of the 36-item WHODAS 2.0 was assessed using Cronbach's alpha. Values ranging from 0.824 to 0.951 were obtained. The interclass correlation coefficients (ICC) were very high. Internal structure of the 36-item WHODAS 2.0 was checked with Confirmatory Factor Analysis (CFA). RMSEA = 0.069, CFI = 0.963, TLI = 0.96, SRMR = 0.081 proved exactness of original six-dimensional structure of WHODAS 2.0. External validity was assessed by correlating the 36-item WHODAS 2.0 scores with the scores of two previously validated tools: FIQ and BDI. Positive correlations were obtained between the 36-item WHODAS 2.0 and these tools. Based on the conducted research, it has been shown that the 36-item WHODAS 2.0 is a reliable and valid tool for assessing disability in individuals with FM in Poland.