Quantitative Analysis of the Minimum Clinically Important Difference in the Brief Pain Inventory After Total Knee Arthroplasty.

Purpose: Research on the Minimum Clinically Important Difference (MCID) of the Brief Pain Inventory (BPI) following Total Knee Arthroplasty (TKA) is limited. This study addresses this gap by determining the MCID of the BPI for patients undergoing primary TKA.

Patients and methods: This study was designed to quantitatively determine the MCID of the BPI for patients undergoing primary TKA. A prospective cohort of 288 patients was evaluated, with the BPI administered both preoperatively and at a one-year follow-up. The MCID was calculated using two primary approaches: the anchor-based method, considered the gold standard, and the distribution-based method. Additionally, this study explored various calculation approaches within the distribution-based framework, benchmarking them against the anchor-based method. The distribution-based methods included calculations based on Standard Deviation (SD), Effect Size (ES), Standardized Response Mean (SRM), and Standard Error of Measurement (SEM). All statistical calculations were performed using established formulas.

Results: The anchor-based method determined the MCID for BPI pain severity to be 3.9 points, the pain interference dimension to be 5.8 points, and the total score to be 9.7 points. Comparisons with the gold standard highlighted the 0.65ES, 1.96SEM, and 0.5SRM methods as the most suitable approaches for distribution-based MCID estimation.

Conclusion: The MCID for BPI in TKA patients was established using both anchor-based and distribution-based methods. When anchor-based determination is impractical, the distribution-based methods-0.65ES, 1.96SEM, and 0.5SRM-are recommended for MCID calculation.