provided practical guidance on refining the original search in their appendix 2. Such efficiencies included refinements based on the yield of the original search and incorporation of technological advances in searching. Recent guidance from an international panel of authors, editors, clinicians, statisticians, information specialists, other methodologists, and guideline developers considered various aspects of updating reviews, including efficient searching. Many handbooks and guidelines for performing systematic reviews state that search strategies should be updated regularly to keep track of newly added references on the topic. The Methodological Expectations of Cochrane Intervention Reviews (MECIR) standards requires: “Rerun or update searches for all relevant databases within 12 months before publication”.

To maximize the currency of a review, an update of the search is recommended before submission for publication. More recently, an examination of 182 systematic reviews performed at Erasmus Medical Centre showed that the median time between the first search and the appearance of the resulting review in PubMed was 89 weeks (interquartile range, 63–126 weeks). In the same cohort of reviews, 7% were out of date at the time of publication.

In a cohort of journal-published systematic reviews, Cochrane reviews, and health technology assessment reports, the median time lag between the stated last search date and publication was 61 weeks (interquartile range, 33–87 weeks). Performing, writing, and publishing a systematic review take a long time.

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