The meaning of global outcome measures in pain clinical trials: more than just change in pain intensity.

To understand the factors that contribute to patient and physician global outcome ratings and the extent to which receiving different doses of opioids or placebo might influence the importance of these factors better. A secondary analysis was performed using data from a prospective, multicenter, double-blind placebo-controlled, and active-controlled parallel group dose-ranging study comparing the efficacy of oxymorphone extended release (ER) 20 mg (ER20, N=121); oxymorphone ER 40 mg (ER40, N=121); oxycodone controlled release 20 mg (Oxy20, N=125); and placebo (N=124) in a sample of patients with osteoarthritis. We performed 2 regression analyses to identify the predictors of pretreatment to posttreatment improvement in patient and physician global ratings of arthritis status. Improvement in global ratings of arthritis status was strongly associated with a decrease in pain intensity. Pretreatment to posttreatment improvement in physical and psychological functioning made independent contributions to the prediction of both criterion variables. The findings underscore the importance of change in pain intensity as a key correlate of ratings of global improvement. However, pain intensity is not the only important factor. In the current sample, improvement in both physical and psychological functioning made independent contributions to improvements in ratings of osteoarthritis status, supporting global ratings as assessing multicomponent domains. Overall, the findings suggest that when a patient or physician reports that the patient is "doing better," the patient is likely reporting less pain intensity and engaging in more physical activity and feeling better emotionally.