The first task for the review team is to determine the purpose of the review revision. If the aim is to simply conduct an update following the existing methods, the review team should notify CEE of their intent before beginning to update the searches. Updating the searches will simply involve re-running them as per the original review or map. Update searches can often be filtered by publication year: a small overlap with the original search is recommended to allow for time lags in the indexing of studies and for searches that covered only part of a calendar year.
If any aspects of the methods or analysis need to be improved or upgraded (for example, to take into account developments in the CEE guidelines or any recommendations identified by the original reviewers in the ‘Limitations of the review/map’ section) then an amendment is necessary and the review team will need to prepare a new protocol for submission to Environmental Evidence (the CEE dedicated journal) specifying the changes. At this stage, the review team must identify whether there is any additional descriptive information or quantitative data that may yet need to be extracted from the studies that were included in the previous review to allow for extended critical appraisal, advanced meta-analysis or inclusion of additional data. This is particularly important since it may have significant resource implications.
Where there is any uncertainty as to whether it is necessary to conduct an update or an amendment, the review team should consult with CEE at the earliest possible opportunity. The review team should also check the original systematic review or map report to determine what data or information are available to them, and in which formats. For example, if original EndNote files are available it may make removing duplicates from updated searches easier than if references are only presented in tables, as lists or even in hard copy. Depending on the composition of the review team, it may be desirable to assess consistency of screening activities on samples used by the original team (if available) to ensure comparability in the application of the inclusion criteria.
Once the update or amendment is underway, the process is similar to that of conducting a new systematic review or map, and guidance on the process should be sought from the relevant sections of the current CEE guidelines (see http://www.environmentalevidence.org). A report of an update may be relatively brief, especially where no new studies have been identified, whereas an amendment will require a more comprehensive report. As per the Cochrane Handbook for Systematic Reviews of Interventions, a ‘What’s new?’ table could usefully be included to help highlight to readers what has changed [14], or the review team could simply include a bulleted section in the text. Authors should seek to ensure transparency and repeatability by documenting any deviations from the protocol and by providing additional files as supplementary information, and in their native file formats (i.e. the formats used to produce and edit the files) where possible. It is also helpful to use a modified flowchart to show how additional results have been captured and incorporated in with the original results (see Fig. 2).
Review authors need to communicate the findings of their updated or amended review or map to ensure that end users are aware that an update has been completed. As such, authors may wish to produce an update brief document for publication alongside their review in Environmental Evidence (perhaps as supplementary information or within the review report itself), for example, that highlights the advances made by the new version and could be communicated to relevant stakeholder communities.