Context: When diagnosed with advanced cancer, patients may perceive their situation as an injustice. The Injustice Experience Questionnaire (IEQ) is a 12-item measure of perceived unfairness originally developed for patients with chronic pain. The factor structure, reliability, and validity of the IEQ in patients with cancer have not been assessed.
Objectives: To examine the factor structure, internal consistency, and construct validity of the IEQ in patients with advanced cancer.
Methods: Patients with advanced lung or prostate cancer (N = 201) were recruited from academic and public clinics in Indianapolis, IN. Patients completed the 12-item IEQ and other measures of psychological processes and distress. IEQ instructions were modified to focus on cancer-related perceived injustice. Confirmatory factor analysis (CFA) was used to examine the dimensionality of the measure. Internal consistency reliability and construct validity were examined.
Results: CFA showed that the original IEQ's 2-factor structure had an adequate fit (RMSEA = 0.07, CFI = 0.96, SRMR = 0.05). The factors included Severity/irreparability and Blame/unfairness. Internal consistency was excellent (α = 0.92, ω = 0.94). The IEQ showed significant positive associations with physical and psychological symptoms (rs = 0.20 - 0.65, Ps < 0.05). The IEQ also showed significant negative associations with quality of life and acceptance of cancer (rs=-0.51 - -0.46, Ps < 0.05).
Conclusion: Findings provide preliminary support for using the IEQ in patients with advanced cancer. Future research should assess the sensitivity of the IEQ to change in an interventional context.
Keywords: Advanced cancer; Factor analysis; Perceived injustice; Psychometrics; Reliability; Validity.
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