Network meta-analysis (NMA)

A network meta-analysis (NMA) is a statistical method using both direct and indirect evidence (conventionally from randomised controlled trials) to estimate the comparative efficacy and/or safety of a number of interventions with each other. An NMA is a specific type of indirect treatment comparison in which the trials all connect via one or more common comparators. An NMA will usually contain multiple treatments and multiple sources of evidence. Typically, a systematic review is used to assemble all trial evidence for efficacy/safety of the interventions of interest in the population/condition and outcome measure of interest into an evidence network that will inform the NMA. At this stage, the comparability of populations, duration, outcome definitions and the feasibility (see feasibility assessment) of the statistical analysis for the NMA are assessed. The reported differences in the outcome measure between interventions (and corresponding measure of uncertainty) in each trial are combined using Monte-Carlo Markov chain methods. In this way, the benefit of randomisation in each source study is preserved when undertaking the NMA.