Abstract
The use of the Injustice Experience Questionnaire (IEQ) in psychological assessment of individuals with chronic pain is supported by research. The psychometric properties of the Swedish version, the IEQ-S, has not yet been evaluated. Hence, the aim was to investigate structural validity, and concurrent criterion validity of the IEQ-S against the Work Ability Index (WAI), the Pain Catastrophizing Scale (PCS-SW), the Patient Health Questionnaire 9-item depression module (PHQ-9), and the Generalized anxiety disorder 7-item scale (GAD-7). Internal consistency and test-retest reliability were also studied. Sixty-five participants, referred to a University hospital, with a pain duration over three months were consecutively sampled. They completed the IEQ-S at admission and again within six weeks. A confirmatory factor analysis was performed for the study of structural validity. Concurrent criterion validity was evaluated using Spearman's correlation coefficient. Internal consistency reliability for the full IEQ-S was calculated using the Cronbach's alpha. Test-retest reliability was calculated using an Intraclass Correlation Coefficient (ICC). The median total score (0-48, where high scores indicate high levels of injustice) at admission (test 1) was 27.0 (n=64), 25th percentile=15.3, 75th percentile=37.8, range=3-48 points. A one-factor model was supported with item-loadings between 0.67-0.92. Spearman's correlation coefficient between the IEQ-S and the WAI (n=56) was rS =-0.46; the PCS-SW (n=63) was rS =0.68, the PHQ-9 (n=64) was rS =0.50 and the GAD-7 (n=64) was rS =0.57, p<0.01. Cronbach's alpha was 0.94 (n=64). The ICC was 0.80 (n=55), with a 95% confidence interval, ranging between 0.69-0.88. Our study supported structural validity and concurrent criterion validity of the IEQ-S against other measures of psychological constructs and work ability. It also supported the internal consistency reliability of the IEQ-S and the test-retest reliability with a retest interval up to six weeks, was good. These findings support the use of the IEQ-S as an adjunct tool to assess appraisals of injustice in patients with chronic pain who are referred to tertiary care in Sweden. The added value might be identification of those who are at risk for slow or no improvement in their pain condition over time, and sick-leave, but this has to be confirmed in future studies. EPN Uppsala D-No 2016-376.
Highlights
Perceived injustice has been conceptualized as “an appraisal cognition or set of cognitions comprising elements of blame, magnitude of loss and irreparability of loss” [1]
Eight participants were excluded from the concurrent criterion validity analysis between the Injustice Experience Questionnaire (IEQ)-S and the Work Ability Index (WAI), whereof five participants had not answered the WAI, two participants had not answered a majority of the WAI questions and one participant was over age 74
This study has contributed with new information about the psychometric properties of the Injustice Experience Questionnaire – Swedish version (IEQ-S), for patients with chronic pain referred to tertiary care in Sweden
Summary
Perceived injustice has been conceptualized as “an appraisal cognition or set of cognitions comprising elements of blame, magnitude of loss and irreparability of loss” [1]. The research area of perceived injustice is relatively novel, recent research suggests that perceived injustice may have a significant negative impact on painrelated outcomes [3] Sullivan et al [1] developed the Injustice Experience Questionnaire (IEQ) to measure. Ahlqvist Lindqvist et al.: The Swedish version of the injustice experience questionnaire perceived injustice associated with musculoskeletal injury. Perceived injustice does arise in an injury context but is present in chronic pain conditions that have a more insidious onset [4]. Perceived injustice among patients having work disabilities, musculoskeletal conditions, has been shown to correlate with pain severity, catastrophizing, fear of movement, perceived disability and depression [1]. The IEQ has been suggested to add to other measures by its unique ability to predict work disability [1]. Research has supported the construct validity as well as the test-retest reliability of the IEQ and has shown that the measure might be a useful complement to psychosocial assessment of individuals with chronic pain [1]
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