Background: Population mean changes from clinical trials are difficult to apply to individuals in clinical practice. Responder analysis may be better, but needs validating for level of response and treatment duration.
Methods: We obtained the number of patients with pain relief over baseline (≥15%, ≥30%, ≥50%, ≥70%) at two, four, eight, and 12 weeks of treatment, using the WOMAC 100 mm visual analogue pain subscale score for each treatment group of seven randomised, placebo-controlled trials of etoricoxib in osteoarthritis lasting six weeks or longer. Dropouts were assigned 0% improvement from baseline from then on. Numbers needed to treat (NNTs) were calculated at each level of response and time point.
Results: 3,554 patients had placebo, etoricoxib 30 mg and 60 mg, celecoxib 200 mg, naproxen 1,000 mg, or ibuprofen 2,400 mg daily. Response rates fell with increasing pain relief; 60-80% experienced minimally important pain relief (≥15%), 50-60% moderate pain relief (≥30%), 40-50% substantial pain relief (≥50%), and 20-30% extensive pain relief (≥70%). NNTs for etoricoxib, celecoxib, and naproxen were stable over 2-12 weeks. Ibuprofen showed lessening of effectiveness with time.
Conclusion: Responder rates and NNTs are reproducible for different levels of response over 12 weeks, and have relevance for clinical practice at the individual patient level. An average 10 mm improvement in pain equates to almost 1 in 2 patients having substantial benefit.