COPM Responsiveness and Clinically Important Change

Responsiveness of the COPM refers to its ability to detect statistically significant and clinically important changes in perceived occupational performance over time. Studies completed over the past 30 years provide much evidence that the COPM detects statistically significant (beyond chance) changes over time (Law et al., 2014; Boyer et al., submitted).
Establishing minimal clinically important change is more challenging than examining statistically significant changes. Minimal clinically important change refers to the smallest change that is perceived by clients to be important and have a positive impact on their function (Page, 2014). Several approaches can be used to evaluate the minimal clinically important change of a measure (Jaeschke, Singer & Guyatt, 1989). In the case of the COPM, it can be evaluated by:

1. Using the opinions of researchers, clinicians and clients to define what constitutes clinically important change (opinion-based approach);
2. Comparing change on the COPM to client’s, therapist’s, and family’s ratings of change in function (known as the anchor-based method); and
3. Comparing change on the COPM to measures of variability such as the standard deviation and/or standard error of the mean (SEM) (distribution-based approach)

In previous manuals of the COPM, it has been stated that a change of 2 points or more is a clinically important difference (Law et al., 2014). This level of change initially came from program evaluation research in an adult mental health setting (N=49) (Mirkolpolous & Butler, 1994). In that study, a change of 2 points on the COPM scales was established as the minimal clinically important standard for the program (opinion-based approach). Results demonstrated that 78% (38 of 49) of the clients reported changes of 2 points or greater on both COPM scales.

Recent studies of responsiveness have used an anchor-based method to calculate the area (AUC) under the Receiver Operating Curve (ROC). An AUC greater than .50 indicates a measure is responsive in differentiating clients whose COPM scores improved versus those who did not improve (de Groot et al., 2006). Eyssen et al. (2011), using this approach, found that change scores of 0.9 for performance and 1.9 for satisfaction corresponded to clients indicating that their occupational performance problems were resolved. The AUC was between 0.79 to 0.85. Tuntland et al. (2016), also using an anchor-based approach, found that older adults receiving rehabilitation services perceived “a little improvement” with score changes of 3 or greater points for performance and 3.2 or greater points for satisfaction.

Enemark Larsen, Wehberg, & Christensen (2021) examined responsiveness in a population of 88 clients with orthopedic knee and ankle problems or receiving general rehabilitation. The AUC for changes of 3.1 points in performance and 3.0 points in satisfaction were 0.76 and 0.75 indicating high levels of responsiveness. Based on optimal cut points for the AUC, they recommend a minimal important change score of 3.5 points for both performance and satisfaction.

Cut off change scores for the COPM in recent research have been higher than the 2 points cited in previous COPM manuals. These results may reflect clinically important change in different populations and contexts or could also be the result of setting an “improvement” standard at a high level to ensure that change has occurred.

An example of a distribution-based approach comes from a study by the COPM authors, involving 219 occupational therapists randomly selected from the Canadian Association of Occupational Therapists’ database (Law et al., 1994). Page (2014) has stated that “Minimal important changes must be beyond the error of the measuring device to ensure clinical changes were not due to measurement error.” In results from 139 clients across several practice areas, mean change scores were  >1.5 times the standard deviation for both performance and satisfaction scales (3.23 for performance and 2.82 for satisfaction), about 18-28 times the SEM. (p. 729). In a randomized controlled trial comparing child-focused with context-focused therapy for young children with CP (Law et al., 2011), change scores on the COPM of 3.8 for performance and 4.3 for satisfaction were 9.5 – 10.2 times the SEM.

Table 4 summarizes the findings of studies that have examined the responsiveness and minimal important clinical change for the COPM. 

Table 4: Studies of the COPM for Responsiveness

The results of research completed over the past 30 years clearly indicate that the COPM is a responsive measure, that is, it detects statistically significant changes (beyond chance) in perceived occupational performance over time. Evidence also indicates that the COPM measures clinically important changes in occupational performance. The key challenge is determining the level of important change and approaches to evaluating change to be used. While previous versions of the COPM manual have indicated that 2 points or more is considered clinically important, it is important to note that it is now generally considered that it is “not plausible that the minimal important change (MIC) is constant” (Tuntland et al., 2016, p. 412). Rather, there is likely to be a range of clinically important differences based on the population, type of occupational performance problems and the context in which clients receive intervention (Eyssen et al., 2011; Page, 2014; Tuntland et al., 2016). Increased research and evidence about minimal important change for the COPM is important to continue to do and hopefully, will increase over time.

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