When a Cochrane review is updated, the search process (i.e. deciding which databases and other sources to search for which years) will have to be reviewed. Those databases that were previously searched and are considered relevant for the update will need to be searched again. The previous search strategies will need to be updated to reflect issues such as: changes in indexing such as the addition or removal of controlled vocabulary terms (MeSH, EMTREE etc); changes in search syntax; comments or criticisms of the previous search strategies. If any of the databases originally searched are not to be searched for the update this should be explained and justified. New databases or other sources may have been produced or become available to the review author or Trials Search Co-ordinator and these should also be considered.
Caution should be exercised with the use of update limits when searching across MEDLINE-indexed and un-indexed records simultaneously such as in PubMed or in the Ovid MEDLINE ‘In-Process & Other Non-Indexed Citations and Ovid MEDLINE 1950 to Present’ file. Where possible, separate files should be selected and searched separately, such as the the Ovid MEDLINE ‘1950 to Month Week X 200X’, and the non-indexed records should be searched for in Ovid MEDLINE ‘In-Process & Other Non-Indexed Citations Month X, 200X’ file. For further guidance on this issue, contact a Trials Search Co-ordinator.