The Evaluation of the Construct and Convergent Validity and Reliability of Psychological Inflexibility in Pain Scale in Individuals With Migraine Headache

Background: The migraine headache is one of the common chronic pains. Recent psychopathological approaches emphasized more on acceptance than the control of pain. Psychological inflexibility in pain scale (PIPS) is a tool to assess pain acceptance. Objectives: The current study aimed at evaluating the psychometric properties of PIPS. Methods: The study sample comprised of 250 individuals with migraine headache. They were selected from patients admitted to neurological ward of Shahid Beheshti Hospital and private neurology clinics in Kashan, Iran in summer 2015. After preparation of the PIPS (translation and back-translation), participants completed the PIPS and chronic pain acceptance questionnaire (CPAQ). The factor structure and correlation of PIPS with CPAQ were examined. Results: The results of exploratory factor analysis (EFA) showed two factors of pain avoidance (10 items) and cognitive fusion factor (six items) for this scale. The confirmatory factor analysis (CFA) confirmed the obtained model in comparison with the original model (group factor analysis (GFA), CFA, and the Tucker-Lewis index (TLI) 0.90; the root mean square error of approximation (RMSEA) 90% confidence interval (CI) = 0.03 - 0.06). Also, the convergent validity of this scale was confirmed with CPAQ (r =.66, P < 0.001). The reliability of the scale by internal consistency and test-retest method was good. Conclusions: The Persian version of PIPS has appropriate psychometric features in Iranian society and it can be used to measure this characteristic.