Minimal Clinically Important Change of Movement Pain in Musculoskeletal Pain Conditions

Abstract

Movement pain, which is distinct from resting pain, is frequently reported by individuals with musculoskeletal pain. There is growing interest in measuring movement pain as a primary outcome in clinical trials, but no minimally clinically important change (MCIC) has been established, limiting interpretations. We analyzed data from 315 participants who participated in previous clinical trials (65 with chronic Achilles tendinopathy; 250 with fibromyalgia) to establish an MCIC for movement pain. A composite movement pain score was defined as the average pain (Numeric Rating Scale: 0-10) during 2 clinically relevant activities. The change in movement pain was calculated as the change in movement pain from pre-intervention to post-intervention. A Global Scale (GS: 1-7) was completed after the intervention on perceived change in health status. Participants were dichotomized into non-responders (GS ≥4) and responders (GS <3). Receiver operating characteristic curves were calculated to determine threshold values and corresponding sensitivity and specificity. We used the Euclidean method to determine the optimal threshold point of the Receiver operating characteristic curve to determine the MCIC. The MCIC for raw change in movement pain was 1.1 (95% confidence interval [CI]: .9-1.6) with a sensitivity of .83 (95% CI: .75-.92) and specificity of .79 (95% CI: .72-.86). For percent change in movement pain the MCIC was 27% (95% CI: 10-44%) with a sensitivity of .79 (95% CI: .70-.88) and a specificity of .82 (95% CI: .72-.90). Establishing an MCIC for movement pain will improve interpretations in clinical practice and research. PERSPECTIVE: A minimal clinically important change (MCIC) of 1.1- points (95% CI: .9-1.6) for movement pain discriminates between responders and non-responders to rehabilitation. This MCIC provides context for interpreting the meaningfulness of improvement in pain specific to movement tasks.

Keywords: Clinical relevance; MIC; Minimal clinically important difference; Movement-evoked pain; Musculoskeletal pain.

Figure 1.

A) Violin plot of raw change in movement pain in each global scale score. B) Violin plot of percent change in movement pain in each global scale score. Median is represented by the bolded line and the IQR is represented by the box for each score category. There is only one data point in the Global Scale Score category of 7 resulting in a mean value.

Figure 2.

A) Scatter plot between raw change in movement pain and global scale score by chronic pain condition Average R² across folds was 0.41 (95%CI: 0.35 – 0.49). B) Scatter plot between percent change in movement pain and global scale score by chronic pain condition. Average R² across folds was 0.35 (95%CI: 0.23– 0.47). Each dot represents individual participant data. (AT- Achilles tendinopathy, FM-Fibromyalgia).

Figure 3.

Receiver Operating Characteristic (ROC) curves for raw and percent change in movement pain. The Area Under the Curve (AUC) for raw change in movement pain was 0.87 (95%CI: 0.83–0.92). The AUC for percent change in movement pain was 0.86 (95%CI: 0.81–0.91). The circles represent the optimal cut-off point of 1.1 as the Minimal Clinically Important Change (MCIC) for raw change in movement pain, and 27% as the MCIC for percent change in movement pain.