Is Their Search Reproducible?

An inadequate search would lead to papers being missed and cause publication bias.

Several electronic databases should be searched (Medline, Embase, Cinhal and the Cochrane library).

Newer search engines such as Google Scholar and the Web of Science can also be used. The Web of Science is particularly good for tracking articles that cite a study you have identified.

A diligent search might also include searching through the references of the papers found on the electronic search (a ‘hand-search’) and contacting well known authors in the field. Doing a really comprehensive search is hard work and best done by a librarian.