Canadian Occupational Performance Measure performance scale: Validity and responsiveness in chronic pain

The construct validity and construct responsiveness of the performance scale of the Canadian Occupational Performance Measure (COPM) was measured in 87 newly admitted patients with chronic pain attending an outpatient rehabilitation clinic. At admission and after 12 wk, patients completed a COPM interview, the Pain Disability Index (PDI), and the RAND 36-Item Health Survey (RAND-36). We determined the construct validity of the COPM by correlations between the COPM performance scale (COPM-P), the PDI, and the RAND-36 at admission. Construct responsiveness was assessed by calculating the correlations between the change scores (n = 57). The COPM-P did not significantly correlate with the PDI (r = -0.260) or with any subscale of the RAND-36 (r = -0.007 to 0.248). Only a moderate correlation was found between change scores of the COPM-P and PDI (r = -0.380) and weak to moderate correlations were found between change scores of the COPM-P and the RAND-36 (r = -0.031 to 0.388), with the higher correlations for the physical functioning, social functioning, and role limitations (physical) subscales. In patients with chronic pain attending our rehabilitation program, the COPM-P measures something different than the RAND-36 or PDI. Therefore, construct validity of the COPM-P was not confirmed by our data. We were not able to find support for the COPM-P to detect changes in occupational performance.