Confirmatory factor analysis of a 4-factor model of chronic pain evaluation

Extending the earlier work of Mikail et al. (1993), a confirmatory factor analysis (CFA; LISREL VII) of a 4-factor model of pain assessment was tested. This model, comprised of the Beck Depression Inventory (BDI) and 13 subscales of the McGill Pain Questionnaire (MPQ) and the West Haven-Yale Multidimensional Pain Inventory (WHYMPI), adequately accounted for the pain experience with minimal overlap. Subjects were 306 outpatient chronic pain patients seen at a multidisciplinary chronic pain clinic. Subscale scores were subjected to CFA procedures that yielded a well-fitting final model that explained 91% of the covariance in the observed data. This final model was derived through an exploratory post-hoc procedure that allowed for correlated errors among subscales of the same instrument. The 4 factors were identified as Affective Distress, Support, Pain Description, and Functional Capacity. Results supported the hypothesis that the MPQ, WHYMPI and BDI are representative of the multidimensionality of the pain experience with minimal overlap among measures. Theoretical and clinical implications of reducing the overlap among existing measures in the assessment of pain patients are discussed.