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Rahim Choudary, Medical Student, Erasmus MC Rotterdam
Other contributors:
Pieter van Doorn, doctoral candidate musculoskeletal diseases at the Department of General Practice, Erasmus MC Rotterdam
Dr. G. Elshout, General Practitioner, assistant professor at the Department of General Practice, Erasmus MC Rotterdam
With great interest, we have read the article "Efficacy of Intra-Articular Hypertonic Dextrose (Prolotherapy) for Knee Osteoarthritis: A Randomized Controlled Trial". We want to compliment the authors for seeking a safer and more effective therapy for the treatment of knee osteoarthritis. However, we had some discussion about the design of the study and interpretation of the results and would like to share them with the authors.
First, as the authors have described in the study, patients were included if they had a score of ≥3 (on an ordinal scale from 0-6) in response to the question: What is the average level of your left/ right knee pain in the past 3 months? We would like to know what the rationale was for the chosen scale, because the chosen scale of 0-6 seems arbitrary.
Second, patients were also excluded if they had a BMI ≥35. A moderation analysis was done and showed no effect of BMI on pain outcome in this study population. But we wondered what the reason was for the exclusion of this group? We would also like to know the specific comorbidities and lifestyle factors of the excluded patients, so that the readers know the factors which have been specifically considered as exclusion criteria in order to make a statement about potential selection bias. Taking these points in consideration, we question the generalizability of the results to the patients with knee osteoarthritis presented in general practice.
This study concludes that intra-articular dextrose prolotherapy injections reduced pain, improved function and quality of life in patients with KOA compared with saline injections. However, we question whether a statement on these separate outcome measures can be concluded from the results of this study. As we understand, the effect size of this study was based on the WOMAC composite score and it is unclear whether the measured difference-in-difference estimates of the separate WOMAC scales actually exceed the minimal clinical important difference (1). We therefore think this conclusion could deserve more nuance.
We hope the authors can respond to our remarks and possibly give us new insights.
1. Devji T, Guyatt GH, Lytvyn L, et al. Application of minimal important differences in degenerative knee disease outcomes: a systematic review and case study to inform BMJ Rapid Recommendations. BMJ Open. 2017;7(5):e015587. Published 2017 May 11. doi:10.1136/bmjopen-2016-015587