Psychometric assessment of the Swedish version of the Injustice Experience Questionnaire among patients with chronic pain

Sammanfattning: Aim: Study the psychometric properties of the Swedish version of the Injustice Experience Questionnaire (IEQ-S) among patients with chronic pain referred to Swedish specialist care. Method: This study was part of a feasibility study for a cohort exploring patients with chronic, non-malignant pain. Sixty-five participants, referred to Pain Center at Uppsala University hospital, with a pain duration over three months at the time of referral, were consecutively sampled. The participants completed the IEQ-S to prepare for their clinical visit and again within six weeks to examine the stability reliability. The Work Ability Index was completed for a concurrent criterion validity analysis. Results: The correlation coefficient between the IEQ-S and WAI (n = 57) was rS = - 0.47, p = < 0.01. The internal consistency reliability for the full IEQ-S was Cronbach’s alpha = 0.94 (n = 64). The stability reliability was calculated using an Intraclass Correlation Coefficient = 0.80 (n = 55), with a 95 % confidence interval ranging between 0.69-0.88. The median total score for IEQ-S measured at admission = 27.0 (n = 64), 25th percentile = 15.3, 75th percentile = 37.8, range = 3-48 points. The mean = 26.2, standard deviation = 13.3. Thirty out of 64 participants (46.9 %) had a total score > 30. Conclusion: This study has contributed with new information about the psychometric properties of the IEQ-S, for patients with chronic pain referred to specialist care in Sweden. The internal consistency of the IEQ-S was high (1), and the stability reliability satisfactory (3). There was a moderate (4), negative, significant relationship between IEQ-S and WAI, high levels of perceived injustice were associated with low work ability in this study. The results support the use of the IEQ-S as an adjunct tool to assess patients with chronic pain referred to specialist care in Sweden, however further research is desirable. This study has also given an insight into how injustice is perceived among patients with chronic pain, however this should be studied in a larger sample.