Riley, Richard DRichard DRileyJackson, DanDanJacksonSalanti, GeorgiaGeorgiaSalanti0000-0002-3830-8508Burke, Danielle LDanielle LBurkePrice, MalcolmMalcolmPriceKirkham, JamieJamieKirkhamWhite, Ian RIan RWhite2024-10-252024-10-252017https://boris-portal.unibe.ch/handle/20.500.12422/155268Summary points: • Meta-analysis methods combine quantitative evidence from related studies to produce results based on a whole body of research • Studies that do not provide direct evidence about a particular outcome or treatment comparison of interest are often discarded from a meta-analysis of that outcome or treatment comparison • Multivariate and network meta-analysis methods simultaneously analyse multiple outcomes and multiple treatments, respectively, which allows more studies to contribute towards each outcome and treatment comparison • Summary results for each outcome now depend on correlated results from other outcomes, and summary results for each treatment comparison now incorporate indirect evidence from related treatment comparisons, in addition to any direct evidence • This often leads to a gain in information, which can be quantified by the “borrowing of strength” statistic, BoS (the percentage reduction in the variance of a summary result that is due to correlated or indirect evidence) • Under a missing at random assumption, a multivariate meta-analysis of multiple outcomes is most beneficial when the outcomes are highly correlated and the percentage of studies with missing outcomes is large • Network meta-analyses gain information through a consistency assumption, which should be evaluated in each network where possible. There is usually low power to detect inconsistency, which arises when effect modifiers are systematically different in the subsets of trials providing direct and indirect evidence • Network meta-analysis allows multiple treatments to be compared and ranked based on their summary results. Focusing on the probability of being ranked first is, however, potentially misleading: a treatment ranked first may also have a high probability of being ranked last, and its benefit over other treatments may be of little clinical value • Novel network meta-analysis methods are emerging to use individual participant data, to evaluate dose, to incorporate “real world” evidence from observational studies, and to relax the consistency assumption by allowing summary inferences while accounting for inconsistency effectsen600 - Technology::610 - Medicine & health300 - Social sciences, sociology & anthropology::360 - Social problems & social servicesarticle10.7892/boris.1064792890392410.1136/bmj.j3932