Table 1

Comparison of umbrella reviews and MARDs

Umbrella reviewMARDs
Brief definitionSystematic 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
CompletenessOnly RCTs* are included when these are included in a review/meta-analysisAll RCTs in the domain are included
RecencySome 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)
ConsistencyIncluded reviews/meta-analyses differ in extracted data from the studies and methodologiesSearches and inclusion of RCTs, as well as data extraction are done uniformly
OutcomesOnly outcomes from published reviews/meta-analyses can be usedOther outcomes (such as secondary outcomes, not reported in abstracts) can also be analysed
Accessibility/reusabilityData from umbrella reviews cannot directly be re-used by othersData 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.