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16.6.1  Introduction

Head-to-head comparisons of alternative interventions may be the focus of a Cochrane Intervention review, a secondary aim of a Cochrane Intervention review, or a key feature of a Cochrane Overview of reviews. Cochrane Overviews summarize multiple Cochrane Intervention reviews, typically of different interventions for the same condition (see Chapter 22). Ideally, direct head-to-head comparisons of alternative interventions would be made within randomized studies, but such studies are often not available. Indirect comparisons are comparisons that are made between competing interventions that have not been compared directly with each other: see Section 16.6.2. Multiple-treatments meta-analysis (MTM) is an extension to indirect comparisons that allows the combination of direct with indirect comparisons, and also the simultaneous analysis of the comparative effects of many interventions: see Section 16.6.3.