Use of indirect comparison methods in systematic reviews: a survey of Cochrane review authors.

Because of insufficient evidence from direct comparison trials, the use of indirect or mixed treatment comparison methods has attracted growing interest recently. We investigated the views and knowledge of Cochrane systematic review authors regarding the use of indirect comparison and related methods in the evaluation of competing healthcare interventions. An online survey was sent to 84 authors of Cochrane systematic review reviews between January and March 2011. The response rate was 57%. Most respondents (87%) had heard of/had some knowledge of indirect comparison, and 23% actually used indirect comparison methods. Some were suspicious of the methods (9%). Most authors (89%) felt they needed more training, especially in assessing the validity of indirect evidence. Almost all felt that the validity of indirect comparison could potentially be influenced by a large number of effect modifiers. Many reviewers (76%) accepted that indirect evidence is needed as it may be the only source of information for relative effectiveness of competing interventions, provided that review authors and readers are conscious of its limitations. Time commitment and resources needed were identified as an important concern for Cochrane reviewers. In summary, there is an acceptance of the increasing demand for indirect comparison and related methods and an urgent need to develop structured guidance and training for its use and interpretation.