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Roth and Shainhouse¹ reported in the ARCHIVES a well-designed randomized controlled trial on efficacy and safety of a topical diclofenac solution in the treatment of primary osteoarthritis of the knee. For clinical implementation we argue that additional information is needed.

In the sample size calculation, the authors state that they wanted to detect a clinically significant difference of 2 (SD of 4.5) in the change in Western Ontario McMaster Universities LK3.1 OA Index (WOMAC) pain dimension scores. To detect this difference, they needed a sample size of at least 80 in each treatment arm, but they decided to use a sample size of 200 patients (100 per treatment arm) to allow for a nonevaluable rate of 20%. In the trial, however, they included 326 patients, leading to 322 evaluable patients for the intent-to-treat analysis (163 in the topical diclofenac group and 159 in the vehicle-control group). Without any explanation . . . [Full Text of this Article]

AUTHOR INFORMATION
Sita M. A. Bierma-Zeinstra, PhD; Janneke N. Belo, MD, MSc; Siep Thomas, MD, PhD

RELATED ARTICLE

Efficacy and Relevance of Topical Diclofenac for Osteoarthritic Pain—Reply
Sanford H. Roth and J. Zev Shainhouse
Arch Intern Med. 2005;165(5):589-590.
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