Further validation of a measure of injury-related injustice perceptions to identify risk for occupational disability: a prospective study of individuals with whiplash injury.

Purpose: Emerging evidence suggests that perceptions of injustice negatively impact return to work following whiplash injury. The Injustice Experiences Questionnaire (IEQ) is a recently developed measurement tool that may be used to assess injury-related perceptions of injustice following injury. To date, although research has supported the predictive validity of the IEQ, a clinical cut off for interpreting this measure has not been established. Increased support for the validity and clinical interpretation of the IEQ represents a first step towards identifying patients that might benefit from targeted intervention to mitigate the impact of perceived injustice.
Methods: The IEQ was completed by 103 whiplash-injured patients upon commencement and completion of a standardized multidisciplinary rehabilitation program. One year later, individuals reported on their employment activity, pain severity, and use of narcotics. A receiver operating characteristic (ROC) curve analysis was conducted to identify the post-treatment IEQ score that was optimally associated with unemployment status at the follow-up. Secondary ROC curve analyses examined IEQ scores best associated with high pain severity and narcotic use 1 year following treatment.
Results: Results indicated that IEQ scores significantly discriminated individuals who returned and did not return to work at the follow-up. An IEQ score of 19 optimally identified participants in terms of follow-up employment status. IEQ scores at the end of treatment also discriminated individuals with high and low pain severity ratings and narcotic use status at the follow-up. Post-treatment IEQ scores of 18 and 20 optimally identified participants who had high pain severity ratings and who were using narcotics at the follow-up, respectively.
Conclusions: These results further support the validity of the IEQ and provide a guideline for its clinical interpretation in patients with persistent pain and disability following musculoskeletal injury. IEQ scores above the identified cut off may represent a barrier to work return and may warrant targeted intervention.