Psychometric Characteristics of the Persian Version of the Injustice Experience Questionnaire

The present study aimed to determine the psychometric characteristics of the Persian version of the Injustice Experience Questionnaire (IEQ-P). Data were collected from 230 participants (122 females and 108 males between 20 and 60 years of age) with chronic musculoskeletal pain. Principal component analysis was used to test the factor structure of the questionnaire. Construct validity was assessed by investigating Pearson correlations among the IEQ-P and other related questionnaires. Internal consistency was indicated by Cronbach's alpha, and test-retest reliability was examined through the intraclass correlation coefficient (ICC) in 48 participants within a three-week period. To examine the differences in the IEQ-P total scores by categorical independent variables, the Kruskal-Wallis test was used. A two-component solution was yielded with good internal consistency (Cronbach's alpha .86). The IEQ-P was correlated significantly with the Pain Catastrophizing Scale (PCS), r = .62, p < .01; McGill Pain Questionnaire (MPQ), r = .44, p < .01; Pain Disability Index (PDI), r = .5, p < .01; Tampa Scale for Kinesiophobia (TSK), r = .48, p < .01; and Beck Depression Inventory II (BDI-II), r = .4, p < .01. Regression analyses revealed that the IEQ-P contributed significant unique variance to the prediction of pain severity, beta = .28, p < .001; self-report disability; beta = .26, p < .001; and depression, beta = .21, p < .001. The obtained results demonstrated an excellent test-retest reliability (ICC = .95). Age, duration of pain, occupation, and educational level were related to the IEQ-P total scores. The IEQ-P was found to be a reliable and valid assessment tool.