abstract
- The calculation of sample size for clinical trials requires knowledge of the standard deviation (SD) of index variables. There are no published lists of SD and it is difficult to locate variance estimates based on relevant populations. In this study we used standardized procedures to determine in 60 patients with osteoarthritis (OA) of the knee the standard deviation of key outcome measures recommended in current Food and Drug Administration and European League Against Rheumatism guidelines for OA clinical trials. These tables will be useful to clinical researchers in selecting outcome measures as well as for calculating sample size requirements for future clinical studies in OA.