OoRs can be completed more quickly and require fewer resources than IRs, but may not give a complete answer to the question of interest, due to the restrictions on the search strategy and availability of data (as these are extracted from IRs). To make the best use of available resources while preparing reviews of high quality and of relevance to the medical decision-making the following process has been suggested and could be included in the protocol when a comparison of multiple interventions is being planned.

1. State clearly the research question, which should be based on clinical need and not the availability of reviews or studies. Include interventions that could reasonably be randomized against each other.
2. Start with an OoR: search for Cochrane Reviews that meet the inclusion criteria.
3. If possible and useful, extract the study-level data from the Cochrane reviews.
4. If possible and useful, extend the search to non-Cochrane reviews
5. If possible and useful, extend the search to individual studies, either in order to add one or more interventions, or in order to update existing systematic reviews.
6. Determine if trials contain sufficient data to perform a MTM, and enough information to judge that the assumptions of MTM are plausible. If yes, do it.
7. If resources permit (funding, statistical support) and/or the topic is of priority for the CRG, extend the OoR to an IR for multiple interventions. This would involve a search for individual studies and extraction of all data at the study level (in some cases it may be possible and appropriate to use the data extracted from reviews in step 2). If judged appropriate, do a MTM.

Depending on the nature of the research question, the available resources and the CRG priorities, reviewers could go directly to step 7.

Other sections of this report:

Addressing multiple interventions in Cochrane Intervention Reviews

Addressing multiple interventions in Cochrane Overviews of Reviews

Clarification of the distinction between Intervention Reviews and Overviews of Reviews

Implications of Overviews for authors and editors of Intervention Reviews

Role of the Cochrane Comparing Multiple Interventions Methods Group

Creation of Working Groups to tackle methodological and practical issues in comparing multiple interventions

Summary of recommendations