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Getting carried away: a note showing baseline observation carried forward (BOCF) results can be calculated from published complete-cases results

International Journal of Obesity volume 36, pages 886–889 (2012)Cite this article

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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References

  1. Elobeid MA, Padilla MA, McVie T, Thomas O, Brock DW, Musser B et al. Missing data in randomized clinical trials for weight loss: scope of the problem, state of the field, and performance of statistical methods. PLoS One 2009; 4(8): e6624.

    Article  Google Scholar 

  2. Gadbury GL, Coffey CS, Allison DB . Modern statistical methods for handling missing repeated measurements in obesity trial data: beyond LOCF. Obes Rev 2003; 4(3): 175–184.

    Article  Google Scholar 

  3. National Research Council. The Prevention and Treatment of Missing Data in Clinical Trials. The National Academies Press: Washington, DC, 2010.

  4. Cox T, Affuso O, Kaiser K, Ingram K, Robertson H, Allison D . Reporting quality of obesity randomized controlled trials: a preliminary review. Proceedings of the International Association for the Study of Obesity, July 2010, International Congress on Obesity, Stockholm, Sweden.

  5. Moher D, Hopewell S, Schulz KF, Montori V, Gotzsche PC, Devereaux PJ et al. CONSORT 2010 explanation and elaboration: updated guidelines for reporting parallel group randomised trials. BMJ 2010; 340: c869.

    Article  Google Scholar 

  6. Shao J, Jordan DC, Pritchett YL . Baseline observation carry forward: reasoning, properties, and practical issues. J Biopharm Stat 2009; 19: 672–684.

    Article  Google Scholar 

  7. Ware JH . Interpreting incomplete data in studies of diet and weight loss. N Engl J Med 2003; 348: 2136–2137.

    Article  Google Scholar 

  8. Kenward MG, Molenberghs G . Last observation carried forward: a crystal ball? J Biopharm Stat 2009; 19: 872–888.

    Article  Google Scholar 

  9. Liu-Seifert H, Zhang S, D’Souza D, Skljarevski V . A closer look at the baseline-observation-carried-forward (BOCF). Patient Prefer Adherence 2010; 4: 11–16.

    PubMed  PubMed Central  Google Scholar 

  10. Gaullier JM, Halse J, Hoivik HO, Hoye K, Syvertsen C, Nurminiemi M et al. Six months supplementation with conjugated linoleic acid induces regional-specific fat mass decreases in overweight and obese. Br J Nutr 2007; 97: 550–560.

    Article  CAS  Google Scholar 

  11. Keogh JB, Brinkworth GD, Noakes M, Belobrajdic DP, Buckley JD, Clifton PM . Effects of weight loss from a very-low-carbohydrate diet on endothelial function and markers of cardiovascular disease risk in subjects with abdominal obesity. Am J Clin Nutr 2008; 87: 567–576.

    Article  CAS  Google Scholar 

  12. Berry W . Understanding Regression Assumptions. Sage Publications: Thousand Oaks, CA, 1993.

    Book  Google Scholar 

Download references

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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Authors and Affiliations

  1. Department of Biostatistics, University of Alabama at Birmingham, School of Public Health, Birmingham, AL, USA

    K A Kaiser, T M Beasley & D B Allison

  2. Department of Epidemiology, University of Alabama at Birmingham, School of Public Health, Birmingham, AL, USA

    O Affuso

  3. Nutrition Obesity Research Center, University of Alabama at Birmingham, Birmingham, AL, USA

    K A Kaiser, O Affuso & D B Allison

Authors
  1. K A Kaiser
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  2. O Affuso
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  4. D B Allison
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Correspondence to D B Allison.

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The authors declare no conflict of interest.

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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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