Indirect [[evidence]], also sometimes referred to as circumstantial evidence, is a fact or set of facts that, if true, allow a person can infer the fact at issue.
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[[Network meta-analysis]] (NMA) is a relatively recent development, which extends principles of [[meta-analysis]] to the [[evaluation]] of multiple [[treatment]]s in a single analysis. This is achieved by combining the direct and [[indirect evidence]]. [[Direct evidence]] refers to evidence obtained from [[randomized control trial]]s (RCTs); for example, in a trial comparing treatments A and B, direct evidence is the estimate of relative effects between A and B. [[indirect evidence]] refers to the evidence obtained through one or more common comparators.

in the absence of RCTs that directly evaluate A and B, interventions A and B can be compared indirectly if both have been compared to C in studies (forming an A-B-C “loop” of evidence). The combination of [[direct evidence]] and [[indirect evidence]] is called [[mixed evidence]].