Retrospective analyses versus RCTs: comparing like with like?
Ralf Baron,1 Lieven Nils Kennes,2 Christian Elling3
1Division of Neurological Pain Research and Therapy, Department of Neurology, University Hospital of Schleswig-Holstein, Kiel Campus, Kiel, 2Department of Economics and Business Administration, University of Applied Sciences Stralsund, Stralsund, 3Grünenthal GmbH, Medical Affairs Europe and North America, Aachen, Germany
In their recent retrospective analysis assessing oxycodone/naloxone (OXN) vs. tapentadol (TAP) treatment for chronic low-back pain with a neuropathic component, Ueberall and Mueller-Schwefe1 compare their results to the findings of an earlier phase 3b/4 study.2 In our opinion, a proper comparison to the prospective, randomized, controlled, open-label study by Baron and colleagues is scientifically not appropriate. Although Ueberall and Mueller-Schwefe use the terms “prospective,” “randomly,” and “blinded” and refer to the PROBE design (prospective, randomized, open-label, blinded endpoint),3 their database study is retrospective, nonrandomized, and nonblinded with the treatment choice left to the discretion of the physicians. In this context, the use of the term “intention-to-treat (ITT) population” is inappropriate because ITT is unambiguously defined as including all randomized subjects and thus inseparable from true randomization (ICH E9).4
Michael A Ueberall,1 Gerhard H H Mueller-Schwefe2
1Institute of Neurological Sciences, Nuernberg, 2Interdisciplinary Center for Pain and Palliative Care Medicine, Goeppingen, Germany
Thank you for the opportunity to reply to the letter of Baron et al. and to discuss their objections concerning our analysis of data from the German Pain Registry. As we have described in our publication,1 the data for our analysis were not prospectively gathered during a doubleblind randomized controlled trial (RCT), but retrospectively taken from the German Pain Registry. This registry is a large database that provides detailed data (based on validated patient questionnaires and physician-recorded information on treatments, and so on) on the routine treatment of pain patients for health care research purposes, but its original intention is to provide patients and physicians a platform to optimize individual treatments during daily life care. Patients with low-back pain (LBP) with a neuropathic component in whom a new treatment with either oxycodone/naloxone (OXN) or tapentadol (TAP) was initiated within a specific period were identified by predefined inclusion and exclusion criteria (as described in our paper). From those patients who fulfilled the enrollment criteria for analysis, we then took a random sample to guarantee an unbiased patient selection for analysis and evaluated the effects of both treatments over a 12-week observation period in a blinded fashion.
View original paper by Ueberall and Mueller-Schwefe.
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