The main characteristic that distinguishes IRs from OoRs is the focus of the search. IRs perform a comprehensive search for all relevant primary studies, while OoRs find studies by searching for Cochrane Reviews or other systematic reviews. Consequently, the data extracted for IR are always study-specific data. Currently, pair-wise meta-analyses are used in IRs to compare interventions, but statistical synthesis using MTM could also be done in many cases, provided that the assumptions of this approach are fulfilled. The following table attempts to clarify the differences between IRs and OoRs.
Review type | Focus of search strategy | Focus of data collection | Focus of statistical synthesis | Comment |
Intervention Review (IR) | Trials | Original trial reports | Trial data | A new review may be planned around a MTM (or indirect comparisons) |
Overview of Reviews (OoR) | Reviews | Review reports (meta-analysis summary estimates from the reviews); or possibly original trial data | Meta-analysis summary estimates or trial data | Synthesis may involve indirect comparisons based on meta-analysis results, or re-analysis of trial data from either review reports or trial reports |
Other sections of this report:
Addressing multiple interventions in Cochrane Intervention Reviews
Addressing multiple interventions in Cochrane Overviews of Reviews
Implications of Overviews for authors and editors of Intervention Reviews
A sequential approach for undertaking reviews that compare multiple-interventions
Role of the Cochrane Comparing Multiple Interventions Methods Group