Comparison of umbrella reviews and MARDs
| Umbrella review | MARDs | |
| Brief definition | Systematic review of systematic reviews in a specific research domain (not necessarily covered by one PICO) | Living systematic review covering a specific research area (not covered by one PICO) |
| Living versus ‘one-off’ systematic review | ‘One-off’ | Living systematic review |
| Completeness | Only RCTs* are included when these are included in a review/meta-analysis | All RCTs in the domain are included |
| Recency | Some delay in recency (two delays: one related to the search dates of the included reviews and one related to the umbrella review itself) | Searches are updated regularly and are therefore as recent as possible (delay only by the searches) |
| Consistency | Included reviews/meta-analyses differ in extracted data from the studies and methodologies | Searches and inclusion of RCTs, as well as data extraction are done uniformly |
| Outcomes | Only outcomes from published reviews/meta-analyses can be used | Other outcomes (such as secondary outcomes, not reported in abstracts) can also be analysed |
| Accessibility/reusability | Data from umbrella reviews cannot directly be re-used by others | Data from MARDs are directly accessible and re-usable by others |
*We say RCT for brevity, but this can also be true for other studies, like open trials and observational studies.
MARD, Meta-Analytic Research Domain; PICO, Participants, Intervention, Comparator, Outcome; RCT, randomised controlled trial.