Translation and validation of the Norwegian version of the Injustice Experience Questionnaire

Perceived injustice is a theoretical construct comprising elements of loss, attribution of blame, and sense of unfairness. Patients with chronic pain often report high levels of perceived injustice, which can have negative impact on physiological and psychosocial aspects and treatment outcome. The Injustice Experience Questionnaire (IEQ) is a self-report 12-item questionnaire that shows good reliability and validity in patients with chronic pain. This study aimed to translate, validate, and expand the use of the Norwegian Injustice Experience Questionnaire (IEQ-N) to a chronic pain population.

A mixed-method approach was used to translate and validate the IEQ-N. It was forward-back translated, linguistically validated, and culturally adapted. Individual cognitive debriefing interviews (n=7) and a focus group interview (n=9) was used to explore the patients' experience with- and understanding of the questionnaire. Statistical descriptive, correlational, factor- and regression analyses were used to investigate the IEQ-N validity, reliability, and factorial structure in a large registry sample (n=3,068) of patients with chronic pain.

Patients with chronic pain found the IEQ-N relevant. Registry analyses supported that the IEQ-N had a one-factor structure. The internal consistency was high (Chronbach's alpha=0.92). The construct validity was good, with moderate to strong significant univariate correlation (r=0.29-0.71) (p<0.05) between perceived injustice and related constructs of pain catastrophizing, pain severity, disability, psychological distress, and quality of life. Perceived injustice contributed with significant but small unique variance to pain-related factors (i.e., pain intensity, pain-related disability, psychological distress), but the additional contribution beyond pain catastrophizing was small (0.2-6.7%) (p<0.05).

Patients in the study found the questionnaire relevant for their situation, and easy to understand. This study provides a reliable and valid Norwegian tool to assess perceived injustice in patients with chronic pain.

REK sør-øst, 2016/1942.