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Self-Management Education for Osteoarthritis
- Joshua Chodosh, MD, MSHS;
- Sally C. Morton, PhD;
- Marika J. Suttorp, MS; and
- Paul G. Shekelle, MD, PhD
- From Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, CA 90073; RTI International, Research Triangle Park, NC 27709-2194; and Veterans Affairs Health Services Research and Development Service, RAND Corporation, Santa Monica, CA 90401.
IN RESPONSE:
We thank Drs. Holman and Lorig for their interest in our paper. Regarding their concern about the effect size in 1 study, our calculated effect size is correct according to our methods because it is based on the follow-up means for pain and function in the 2 groups. The effect size listed by Drs. Holman and Lorig in their letter is a “difference of difference” calculation that adjusts for baseline differences in pain and function between the 2 randomized groups in their study. Although this is 1 valid method to analyze the results of an individual article, we prefer not to combine “difference of difference” estimates with follow-up mean estimates in our meta-analyses because of reports that such an approach can increase susceptibility to bias (1). On a practical level, combining just those studies that contained “difference of difference” estimates would decrease the number of studies that can be included in a …
