Embracing the grey: How to systematically search literature not indexed in an electronic database to comprehensively answer pressing global health questions

Background: The importance of synthesizing data from both peer reviewed and grey literature is increasingly recognized as integral to comprehensively answering important global health and development research questions. In this paper, we describe our experience combining traditional search methods along with methods for searching the relevant grey literature relating to the impact of women's participation in economic self-help groups on their empowerment and health in low and middle-income countries. As these types of comprehensive reviews become more prevalent, consensus around clearly defined guidelines for the search process is necessary.

Objective: The purpose of this paper is to demonstrate an inclusive framework for systematically and exhaustively searching the grey literature when conducting reviews that require looking beyond the peer-reviewed and indexed literature of traditional reviews.

Methods: Search guidelines were generated through discussions, trials and shared experiences of a research team conducting a review on women's empowerment and health that required exhaustive grey literature searches. Additionally, the authors held informal discussions with systematic reviewing experts and university librarians on the utility of their novel methods and integrated their feedback. By methodically searching the grey literature, we incorporated more comprehensive findings into the final research conclusions.

Results: We describe several unique methods for embracing the grey literature including conducting specialized search engine queries, hand searching relevant websites and journals, conducting bibliographic back-referencing, developing keyword and program search guidelines, and soliciting feedback from key contacts using online surveys. We present a comprehensive and replicable process for the mixed-method and qualitative review process.