Psychometric properties of the Brief Pain Inventory among patients with osteoarthritis undergoing total hip replacement surgery

BACKGROUND Pain is a cardinal symptom of osteoarthritis (OA) of the hip and important for deciding when to operate. This study assessed the internal consistency reliability, validity and responsiveness of the Brief Pain Inventory (BPI) among patients with OA undergoing total hip replacement (THR). METHODS We prospectively included 250 of 356 patients who were accepted to the waiting list for primary THR surgery. All participants responded to the BPI, WOMAC and SF-36 at baseline and 1 year after surgery. RESULTS Internal consistency reliability (Cronbach's α) was >0.80 for the BPI, the WOMAC and five of the eight SF-36 scales The pattern of associations of the two BPI scales with corresponding and non-corresponding scales of the WOMAC and SF-36 largely supported the construct validity of the BPI. The responsiveness indices for change from baseline to 1 year after THR ranged from 1.52 to 2.05 for the BPI scales, from 1.69 to 2.84 for the WOMAC scales, and from 0.25 (general health) to 2.77 (bodily pain) for the SF-36 scales. CONCLUSIONS The BPI showed acceptable reliability, construct validity and responsiveness in patients with OA undergoing THR. BPI is short and therefore is easy to use and score, though the instrument offers few advantages over and duplicates scales of more comprehensive instruments, such as the WOMAC and SF-36.