Responder analysis and correlation of outcome measures: pooled results from two identical studies comparing etoricoxib, celecoxib, and placebo in osteoarthritis

Objectives: To determine the proportion of responders in two identical osteoarthritis (OA) trials using Outcome Measures in Arthritis Clinical Trials-Osteoarthritis Research Society International (OMERACT-OARSI) criteria and to assess the comparability and correlation of individual component measurements. Methods: Data were pooled from two identical 26-week, double-blind, randomized, parallel, multicenter trials comparing once daily etoricoxib 30 mg (N = 475), celecoxib 200 mg (N = 488), and placebo (N = 244) in patients with OA of the knee or hip. OMERACT-OARSI criteria were (1) improvement in pain or physical function ≥50% and an absolute change ≥20 mm on a 100-mm visual analog scale (VAS); or (2) improvement of ≥20% and with an absolute change ≥10 mm in at least two of the following three categories: pain, physical function, and patient's global assessment. Correlations were assessed between endpoints measured as time-weighted average change from baseline over 12 weeks using Pearson's correlation coefficient (r). Results: There were significantly greater proportions of responders in the etoricoxib (66.2%) and celecoxib (63.5%) groups compared with the placebo group (43.0%; P < 0.001). There was no difference between the two active treatment groups. There was high correlation between pain and physical function (r = 0.903), pain and global assessment (r = 0.778), and physical function and global assessment (r = 0.820). There was high sensitivity (75-87%) and specificity (80-96%) for changes in individual component measurements to predict OMERACT-OARSI responders. Conclusions: Significantly more patients receiving etoricoxib or celecoxib than placebo were OMERACT-OARSI responders. The high correlation between individual scales composing this composite response measurement suggests some redundancies between individual components, particularly between pain and physical function.