A Clinically Significant Difference on the COPM: A Review

Background. The Canadian Occupational Performance Measure (COPM) assists occupational therapists to identify occupational performance problems using a client-centred approach. Since its first publication in 1991, there has been abundant evidence of the ability of the COPM to detect a statistically significant difference as an outcome measure. There has also been a tacit understanding that a difference of 2 points from pre-test to post-test on either Performance or Satisfaction COPM score represents a clinically significant difference. There is however, some confusion about the origins of this claim. Purpose. To ascertain empirical evidence for the claim that a clinically significant difference is a change score ≥2 points. Method. We conducted a scoping review of peer-reviewed literature (1991-2020) for intervention studies using the COPM as an outcome measure and examined intervention type and change scores. Findings. One hundred studies were identified. The COPM was used to assess effectiveness of eight types of occupational therapy interventions. The common belief, however, was not empirically supported that clinical significance can be asserted on the basis of a two-point change in COPM scores. Implications. Further research is needed to test alternative approaches to asserting clinical significance or a minimal clinically important difference.