This policy covers the reporting of search dates in Cochrane Reviews. It is informed by guidance on re-running searches covered in MECIR conduct standard C37. This standard requires that searches for all relevant databases be run (or re-run) within 12 months before publication of the review or review update, and that the results are screened for potentially eligible studies.
For definitions of search types (full, top-up, scoping) see Table below.
Full search – results fully incorporated
Electronic search strategies run in full in all relevant databases AND all search results are assessed for eligibility as included, excluded, or ongoing studies. Only if all reasonable efforts to classify search results have failed should they be placed in ‘Studies awaiting classification.’*
Top-up search – results not fully incorporated
Electronic search strategies run in full in all relevant databases BUT search results are not all assessed for eligibility, instead they are placed in 'Studies awaiting classification'.
Scoping search for updating
Electronic search strategies run in selected databases to determine if an update is required.
|*See R6 and R34 in MECIR; and definition of updating.|
The number of instances where a top-up search is performed and potential new studies are identified but not fully incorporated before publication should remain low. The following examples show how such searches should be described in various sections of a systematic review:
Do not change the 'Date of search' or the 'Assessed as up-to-date' (see Note for editorial base staff) in the Cochrane Review 'Information’ section. Also, if less than 10 trial reports then list here in parentheses and link. For example:
"The search was updated in month/year and n trial reports added to ‘Studies awaiting classification’ (e.g. Bertini 2005; Crowther 2005; Gillen 2004)."
The focus should remain on the text about previous searches (fully incorporated) but the top-up search may be mentioned. For example:
"We searched the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, and CINAHL (June 2013). We updated this search in September 2014, but these results have not yet been incorporated."
The search should be reported as per MECIR reporting standards R34 to 39, including the dates for each source. At the end of the search methods section, it is appropriate to add the following text:
"We performed a further search in [month/year]. Those results have been added to 'Studies awaiting classification' and will be incorporated into the review at the next update."
Do not list all databases and the dates. If a top-up search in reported in this section, only a single month (or range of months) and year should be shown.
This section will differ depending on the review, so add text where it is most appropriate); for example:
"[insert number] study reports from an updated search in [month/year] have been added to 'Studies awaiting classification'."
Acknowledge the potential impact of un-incorporated studies as a source of potential bias, especially if studies concerned are potentially important in terms of sample size or direction of effect; for example:
"We attempted to conduct a comprehensive search for studies, but the fact that [insert number] studies have not yet been incorporated may be a source of potential bias."
This is not an implication for practice as such, but users should be alerted to the issue of un-incorporated studies, particularly if the studies concerned are potentially important in terms of sample size or direction of effect; for example:
"The [insert number] studies in 'Studies awaiting classification' may alter the conclusions of the review once assessed."
One date should be used to reflect the search and full incorporation of all search results into the review; this date is the ‘Date of search’. Standard practice has been to publish the 'Assessed as up-to-date' field and not the 'Date of search'. Until the 'Assessed as up-to-date' field is removed from RevMan these two dates must be the same. If these fields have been completed by a member of the author team, editorial base staff must check that there is agreement between dates.