Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2013 Sep 5:347:f5195.
doi: 10.1136/bmj.f5195.

The effects of excluding treatments from network meta-analyses: survey

Edward J Mills  1 , Steve Kanters, Kristian Thorlund, Anna Chaimani, Areti-Angeliki Veroniki, John P A Ioannidis
Affiliations

The effects of excluding treatments from network meta-analyses: survey

Edward J Mills et al. BMJ. .

Abstract

Objective: To examine whether the exclusion of individual treatment comparators, including placebo/no treatment, affects the results of network meta-analysis.

Design: Survey of networks with individual trial data.

Data sources: PubMed and communication with authors of network meta-analyses.

Study selection and methods: We included networks that had five or more treatments, contained at least two closed loops, had at least twice as many studies as treatments, and had trial level data available. Investigators abstracted information about study design, participants, outcomes, network geometry, and the exclusion of eligible treatments.

Results: Among 18 eligible networks involving 757 randomised controlled trials with 750 possible treatment comparisons, 11 had upfront decided not to consider all treatment comparators and only 10 included placebo/no treatment nodes. In 7/18 networks, there was at least one node whose removal caused a more than 1.10-fold average relative change in the estimated treatments effects, and switches in the top three treatments were observed in 9/18 networks. Removal of placebo/no treatment caused large relative changes of the treatment effects (average change 1.16-3.10-fold) for four of the 10 networks that had originally included placebo/no treatment nodes. Exclusion of current uncommonly used drugs resulted in substantial changes of the treatment effects (average 1.21-fold) in one of three networks on systemic treatments for advanced malignancies.

Conclusion: Excluding treatments in network meta-analyses sometimes can have important effects on their results and can diminish the usefulness of the research to clinicians if important comparisons are missing.

PubMed Disclaimer

Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

Figures

None
Networks included in analysis. The line thickness is proportional to the number of trials comparing the treatments along the edge. Nodes leading to changes in ranks among the top ranked treatments are in large font
See this image and copyright information in PMC

References

    1. Lu G, Ades AE. Combination of direct and indirect evidence in mixed treatment comparisons. Stat Med 2004;23:3105-24.. - PubMed
    1. Mills EJ, Bansback N, Ghement I, Thorlund K, Kelly S, Puhan MA, et al. Multiple treatment comparison meta-analyses: a step forward into complexity. Clin Epidemiol 2011;3:193-202. - PMC - PubMed
    1. Sutton A, Ades AE, Cooper N, Abrams K. Use of indirect and mixed treatment comparisons for technology assessment. Pharmacoeconomics 2008;26:753-67. - PubMed
    1. Wells GA, Sultan SA, Chen L, Khan M, Coyle D. Indirect evidence: indirect treatment comparisons in meta-analysis. Canadian Agency for Drugs and Technologies in Health, 2009.
    1. Act on the Reform of the Market for Medicinal Products (Gesetz zur Neuordnung des Arzneimittelmarktes, AMNOG). Statute 35a (1), S. 6+7, SGB V.

Publication types