Validation of the Brief Pain Inventory in Patients With Low Back Pain.

STUDY DESIGN Cross-sectional psychometric testing in a sample of patients with low back pain (LBP). OBJECTIVE The aim of this study was to examine the construct, convergent, and discriminative validity of the Brief Pain Inventory (BPI) in patients with LBP. SUMMARY OF BACKGROUND DATA The BPI was originally developed to assess cancer pain. Currently, it is commonly used to measure pain intensity and pain interference in patients with malignant or nonmalignant pain. However, the two-factor construct of the BPI has not been confirmed in an LBP population. METHODS A total of 271 patients with LBP completed the BPI and Oswestry Disability Index (ODI) questionnaires. The construct validity (i.e., the two-factor structure: intensity scale and interference scale) of the BPI was determined by confirmatory factor analysis. The convergent validity was investigated by examining the relationships between the BPI scales and the ODI scores. The discriminative validity of the BPI was examined by testing if the BPI scale scores differed among groups of patients with different levels of disability. RESULTS Confirmatory factor analysis partially confirmed the two-factor structure of the BPI for use in patients with LBP. The convergent validity of the BPI was supported by its moderate correlation between the interference scale and the ODI score (ρ = 0.66, P < 0.001), and by its low correlation between the intensity scale and the ODI score (ρ = 0.39, P < 0.001). Finally, both the intensity scale and the interference scale discriminated among patients with varying levels of disability (both P < 0.001). CONCLUSION The two-factor structure of the BPI as a measure of pain intensity and interference in patients with LBP was partially confirmed. Furthermore, our results lend some supports to the convergent validity and discriminative validity of the BPI. LEVEL OF EVIDENCE N/A.