Minimal Clinically Important Changes of Patient-reported Outcome Measures for Acute Postsurgical Pain

Patient-reported outcome measures (PROMs) are essential instruments for assessing postsurgical pain-related outcomes from the patient's perspective. The concept of minimal clinically important difference (MCID) aims to identify the smallest change in PROMs that is meaningful to patients. In this multicenter study, data were used to calculate MCIDs for several PROMs assessing pain intensity and physical function after surgery and to perform a sensitivity analysis.

Data from 2,661 patients undergoing sternotomy, total knee arthroplasty, breast surgery, or surgery related to endometriosis, recruited from 18 centers in 10 European countries, were included in the analysis. Eight PROMs were collected on days 1 and 3 after surgery, assessing pain intensity (at rest, average, worst, during movement, during physiotherapy) and physical function (in bed, during movement, during physiotherapy). MCIDs were calculated using a combination of distribution-based (30% of SD, standard error of the measurement) and anchor-based (calculating the absolute change between day 1 and day 3 for patients reporting "minimal improvement" or "minimal worsening" on 7-point global and specific impression of change scales) methods.

The MCID estimates for pain intensity ranged from 1.2 (at rest) to 1.6 (during activity), while physical function was consistent between 1.5 (in bed) and 1.6 (during physiotherapy) on an 11-point scale. Sensitivity analyses revealed no significant difference in MCID estimates between symptom improvement and worsening for all PROMs. However, baseline pain influenced MCID estimates, with higher baseline pain leading to patients reporting higher changes as meaningful ( e.g. , for pain at rest, MCID mild pain 1.0, MCID severe pain 2.1).

The authors found differences between MCID estimates for eight PROMs related to pain intensity and physical function. Baseline values appear to have a significant impact on what patients consider to be a minimal relevant change, which should be addressed in future studies.