Table 1 Medline, Embase, and Google search strategies

The Medline search strategy involved combinations of free text terms with search terms chosen from the database’s Medical Subject Headings (MeSH) and included: “internet”[Mesh] AND ((“registries”[Mesh] OR registries[Title/Abstract]) AND (trial[Title/Abstract] OR trials[Title/Abstract]). Similarly, the Embase search was based on the terms chosen from the Emtree thesaurus: (‘register’/exp AND ‘internet’/exp AND ‘clinical study’/exp). The Google search, aimed at finding links concerning registries, involved the same keywords as the database searches, in addition to several synonyms. The bibliographies of selected articles were examined to identify additional relevant studies, and several websites were searched for links to additional registries.