title: 'Arm-based' parameterization for network meta-analysis.
abstract: We present an alternative to the contrast-based parameterization used in a number of publications for network meta-analysis. This alternative "arm-based" parameterization offers a number of advantages: it allows for a "long" normalized data structure that remains constant regardless of the number of comparators; it can be used to directly incorporate individual patient data into the analysis; the incorporation of multi-arm trials is straightforward and avoids the need to generate a multivariate distribution describing treatment effects; there is a direct mapping between the parameterization and the analysis script in languages such as WinBUGS and finally, the arm-based parameterization allows simple extension to treatment-specific random treatment effect variances. We validated the parameterization using a published smoking cessation dataset. Network meta-analysis using arm- and contrast-based parameterizations produced comparable results (with means and standard deviations being within +/- 0.01) for both fixed and random effects models. We recommend that analysts consider using arm-based parameterization when carrying out network meta-analyses. © 2015 The Authors Research Synthesis Methods Published by John Wiley & Sons Ltd.
authors.affiliation: ICON Health Economics, Oxford, OX2 0JJ, UK.
authors.forename: Neil
authors.initials: N
authors.lastname: Hawkins
authors.affiliation: ICON Health Economics, Oxford, OX2 0JJ, UK.
authors.forename: David A
authors.initials: DA
authors.lastname: Scott
authors.affiliation: Centre for Health Economics, Alcuin 'A' Block, University of York, York, YO10 5DD, UK. beth.woods@york.ac.uk.
authors.forename: Beth
authors.initials: B
authors.lastname: Woods
mesh_terms: D000465:Algorithms; D002986:Clinical Trials as Topic; D003627:Data Interpretation, Statistical; D006801:Humans; D015999:Multivariate Analysis; D011381:Programming Languages; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D012306:Risk; D016540:Smoking Cessation / Q000379:methods*; D012984:Software; D014029:Tobacco Use Disorder / Q000628:therapy; D000071076:Network Meta-Analysis as Topic
keywords: arm-based parameterization; network meta-analysis; winBUGS