Abstract
Objective:
Randomized controlled trials (RCTs) in obesity are plagued by missing data due to participant dropouts. Most methodologists and regulatory bodies agree that the primary analysis of such RCTs should be based on the intent-to-treat (ITT) principle, such that all randomized subjects are included in the analysis, even those who dropped out. Unfortunately, some authors do not include an ITT analysis in their published reports. Here we show that one form of ITT analysis, baseline observation carried forward (BOCF), can be performed utilizing only information available in a published complete-case (CC) analysis, permitting readers, editors, meta-analysts and regulators to easily conduct their own ITT analyses when the original authors do not report one.
Method:
We mathematically derive a simple method for estimating and testing treatment effects using the BOCF to allow a more conservative comparison of treatment effects when there are dropouts in a clinical trial. We provide two examples of this method using available CC analysis data from reported obesity trials to illustrate the application for readers who wish to determine a range of treatment effects based on published summary statistics.
Conclusion:
Commonly used CC analyses may lead to inflated type I error rates and/or treatment effect estimates. The method described herein can be useful for researchers who wish to estimate a conservative range of plausible treatment effects based on limited reported data. Limitations of this method are discussed.
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Acknowledgements
We thank Dr Kyle Grimes for editorial comments on an earlier version of this manuscript. We also thank the anonymous reviewers for providing helpful suggestions to improve this manuscript. Support: we received support in part by NIH grants R01DK078826, P30DK056336 and T32HL007457. The opinions expressed are those of the authors and not necessarily the NIH or any organization with which the authors are affiliated.
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Dr Allison has received grants, honoraria, donations and consulting fees from numerous food, beverage, pharmaceutical companies, and other commercial and non-profit entities with interests in obesity and randomized controlled trials.
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Kaiser, K., Affuso, O., Beasley, T. et al. Getting carried away: a note showing baseline observation carried forward (BOCF) results can be calculated from published complete-cases results. Int J Obes 36, 886–889 (2012). https://doi.org/10.1038/ijo.2011.25
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DOI: https://doi.org/10.1038/ijo.2011.25
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