We read with great interest the recent article by Case et al,1 but had major concerns regarding the conclusions these authors draw from such a well-performed study. Interestingly, the authors only demonstrate that diclofenac sodium use provides benefit at 2 and 12 weeks in osteoarthritis (OA) compared with baseline using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scale (but not the Lequesne). Wisely, they argue strongly in favor of placebo-controlled, longer-term trials and, in fact, found a significant placebo effect in 2 of the 4 WOMAC subgroups at 12 weeks. In what may represent the authors' bias, however, when presenting their results they do not compare the diclofenac-treated patients at 12 weeks with either the acetaminophen-treated patients or the placebo groups at 12 weeks (they compared acetaminophen with placebo at this time point and found no difference). By simple "eyeball" test, it does not appear that diclofenac use was any more efficacious than placebo at 12 weeks. If this is indeed the case, shouldn't the title of the article be, "The Lack of Efficacy of Acetaminophen or Diclofenac in Treating Symptomatic Knee Osteoarthritis"? As it is now, one might misinterpret their findings to suggest that diclofenac is superior to acetaminophen in this study. Further, it is concerning that a less complete description was given for the reasons for dropout in the diclofenac group compared with the acetaminophen group. Specifically, was drug toxicity a problem?
Christmas C, Moncada L. Interpretation of Therapies for Knee Arthritis. Arch Intern Med. 2003;163(15):1862. doi:10.1001/archinte.163.15.1862-a