Almost half of references in reports on new and emerging nondrug health technologies are grey literature

The research investigated how frequently grey literature is used in reports on new and emerging nondrug health technologies, which sources are most cited, and how grey literature searching is reported.

A retrospective review of references cited in horizon scanning reports on nondrug health technologies-including medical devices, laboratory tests, and procedures-was conducted. A quasi-random sample of up to three reports per agency was selected from a compilation of reports published in 2014 by international horizon scanning services and health organizations.

Twenty-two reports from 8 agencies were included in the analysis. On average, 47% (288/617) of references listed in the bibliographies of the horizon scanning reports were grey literature. The most frequently cited type of grey literature was information from manufacturers (30% of all grey literature references), regulatory agencies (10%), clinical trial registries (9%), and other horizon scans or evidence synthesis reports (9%). The US Food and Drug Administration (FDA) and ClincalTrials.gov were the most frequently cited specific sources, constituting 7% and 8% of grey literature references, respectively. Over two-thirds (15/22) of the analyzed reports provided some details on search methodology; all 15 of these reported searching some grey literature.

In this sample, grey literature represented almost half of the references cited in reports on new and emerging nondrug health technologies. Of these grey literature references, almost half came from three sources: the manufacturers, ClincalTrials.gov, and the FDA. There was wide variation in the other sources cited. Literature search methodology was often insufficiently reported for analysis.