Validation of the modified brief pain inventory-exploratory form in surgery patients

Objective: An exploratory version of the Modified Brief Pain Inventory (mBPI-e) to measure acute post-operative pain, with new items on coughing, breathing, and concentration, was examined for their measurement properties. Study Design: This is a secondary study using data from two randomized clinical trials: general surgery trial (N=1050) and coronary artery bypass graft (CABG) surgery trial (N=1636). The measurements used in the two trials were: 1) mBPI-e; 2) clinician and patient global evaluations of medications; and 3) pain intensity diary. The mBPI-e and pain intensity were collected for 10 days. Clinician and patient global evaluations of medication were collected twice. The analyses conducted were: 1) exploratory factor analysis (EFA); 2) confirmatory factor analysis (CFA); 3) item response theory (IRT); 4) internal consistency; 5) test-retest reliability; 6) concurrent validity; 7) known-group validity; and 8) responsiveness. Results: Pain severity, pain interference, and coughing and breathing factors were identified. Pain severity and pain interference subscale scores were constructed for mBPI-e. IRT analyses showed all items exhibited good item characteristics. Internal consistency was 0.85 for severity and 0.87 for interference. Test-retest reliability was 0.81 for severity and 0.71 for interference. Both severity and interference scores were correlated with diary-based pain intensity ratings (P <.0001). Mean severity and interference scores varied by physician and patient global ratings (P <.05). Severity and interference scores were responsive to changes in pain diary scores and physician global ratings (P <.001). There were no substantive differences in reliability or validity for sub-samples of surgery patients. Conclusions: The original BPI has been used in clinical studies, and the mBPI has demonstrated good reliability and validity in CABG patients. Based on this study, the mBPI-e has also demonstrated good reliability and validity for assessing postoperative acute pain in CABG and general surgery patients.