Objective: Persistent postoperative pain is an acknowledged entity that reduces daily activities. Evaluation of the post-thoracotomy pain syndrome (PTPS) is often measured using traditional pain scales without in-depth questions on pain impairment. Thus, the purpose was to create a procedure-specific questionnaire for assessment of functional impairment due to PTPS.
Methods: Activities were obtained from the literature supplemented by interviews with patients and surgeons. The questionnaire was validated using the Rasch model in order to describe an underlying pain impairment scale.
Results: Four of 17 questions were redundant. The remaining 13 questions from low to intensive activity described functional impairment following persistent pain from thoracotomy and video-assisted thoracic surgery (VATS). No evidence for differential item functioning for gender, age or differences between open or VATS, were found. A generalized log-linear Rasch model including local dependence was constructed. Though local dependence influenced reliability, the test-retest reliability estimated under the log-linear Rasch model was high (0.88-0.96). Correlation with items from the Disability of the Arm, Shoulder and Hand (quick) questionnaire supported validity (γ = 0.46, P < 0.0001), and procedure specificity. The analysis also procured evidence that the pain impairment questionnaire measured 2 qualitatively different pain dimensions although highly correlated (γ = 0.76).
Conclusions: This study presents method, results and validation of a new unidimensional scale measuring procedure specific functional impairment due to PTPS following open surgery and VATS. Procedure specific tools such as this could provide important outcomes measures for future trials on persistent postsurgical pain states allowing better assessment of interventions (250).