title: An approach for modelling multiple  correlated outcomes in a network of  interventions using odds ratios.
abstract: A multivariate meta-analysis of two or more correlated outcomes is expected to improve precision compared with a series of independent, univariate meta-analyses especially when there are studies reporting some but not all outcomes. Multivariate meta-analysis requires estimates of the within-study correlations, which are seldom available. Existing methods for analysing multiple outcomes simultaneously are limited to pairwise treatment comparisons. We propose a model for a joint, simultaneous synthesis of multiple dichotomous outcomes in a network of interventions and introduce a simple way to elicit expert opinion for the within-study correlations by utilizing a set of conditional probability parameters. We implement our multiple-outcomes network meta-analysis model within a Bayesian framework, which allows incorporation of expert information. As an example, we analyse two correlated dichotomous outcomes, response to the treatment and dropout rate, in a network of pharmacological interventions for acute mania. The produced estimates have narrower confidence intervals compared with the simple network meta-analysis. We conclude that the proposed model and the suggested prior elicitation method for correlations constitute a useful framework for performing network meta-analysis for multiple outcomes.
authors.forename: Orestis
authors.initials: O
authors.lastname: Efthimiou
authors.forename: Dimitris
authors.initials: D
authors.lastname: Mavridis
authors.forename: Andrea
authors.initials: A
authors.lastname: Cipriani
authors.forename: Stefan
authors.initials: S
authors.lastname: Leucht
authors.forename: Pantelis
authors.initials: P
authors.lastname: Bagos
authors.forename: Georgia
authors.initials: G
authors.lastname: Salanti
mesh_terms: D001499:Bayes Theorem; D001714:Bipolar Disorder / Q000188:drug therapy; D003627:Data Interpretation, Statistical; D006801:Humans; D015201:Meta-Analysis as Topic; D015233:Models, Statistical; D016017:Odds Ratio; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D016032:Randomized Controlled Trials as Topic