After you have identified a clinically important question, you will want to determine if a systematic review or registered protocol is already available.
A protocol is a formal game plan for research. Its a proposed systematic review in process. If someone else is in the process of researching your exact question, you may want to contact the authors to see where they are in the process to determine your own need to pursue your topic.
A registry of protocols of systematic reviews could assist those planning new reviews and updating existing ones. Easy access to information about ongoing reviews should help to optimise the use of finite resources by enabling funding and commissioning agencies to avoid unnecessary duplication and encourage collaboration. A comprehensive registry could also create opportunities for methodological and other research, both within and across disciplines."Booth, A., Clarke, M., Ghersi, D., Moher, D., Petticrew, M., & Stewart, L. (2011). An international registry of systematic-review protocols. The Lancet, 377(9760), 108–109. http://doi.org/10.1016/S0140-6736(10)60903-8
The Literature Review
A systematic review will include both published and unpublished sources.
No single database covers everything. Even though there may be significant duplication of results across resources, by definition, a Systematic Review requires that you systematically search multiple resources to identify every potential source of data. Depending on your topic you may need to check other resources in addition to the core list of licensed library databases.
The PRISMA Flowchart captures the steps you will need to follow and document as part of your literature review and reporting process. PRISMA has a really helpful online tool to help you generate a graphic of this flowchart, adding the specific information you need to report. You may also download a copy as Word Document or as a pdf.
Grey Literature is any material that can be difficult to track down by conventional research methods, but are generally included as part of your review process.
"In general, grey literature publications are non-conventional, fugitive, and sometimes ephemeral publications. They may include, but are not limited to the following types of materials: reports (pre-prints, preliminary progress and advanced reports, technical reports, statistical reports... etc.), theses, conference proceedings, technical specifications and standards ... and official documents not published commercially (primarily government reports and documents) (Alberani, 1990)." [The Grey Literature Report, The New York Academy of Medicine (NYAM) http://www.greylit.org/about]
Not every online database or catalog is indexed in Google. So while Google & Google Scholar are helpful tools to locate materials in this category, its important to identify specific organizations or government agencies that gather data and publish results in the area you are researching and then search those organizations catalogs etc.. Need help identifying organizations and agencies that produce data in your area of research? Contact a librarian to help you strategize.