Systematic Reviews

In order to be thorough and systematic, multiple databases must be used and grey literature must also be searched if it is applicable. The Cochrane Collaboration recommends searching a minimum of three databases:

• The Cochrane Central Register of Controlled Trials
• MEDLINE (via PubMed or OVID)
• EMBASE (usually searched via Scopus)

The Cochrane Collaboration also specifies that:

• Searches should seek high sensitivity, which may result in relatively low precision.
• Too many different search concepts should be avoided, but a wide variety of search terms should be combined with OR within each concept.
• Both free-text AND subject headings should be used.

Your inclusion/exclusion criteria are extremely important and allow you to make your results more precise after you've conducted a search to find as much as you can that touches on your topic of interest.

Just as in clinical or bench research, a detailed methodology of your search strategy, results and inclusion/exclusion criteria must be included in your review so that it is reproducible. PRISMA standards require you to fill out a flow diagram and provides a helpful checklist to determine if your SR is complete.

• PRISMA Checklist
• PRISMA Flow Diagrams

Remember the evidence pyramid and how few systematic reviews and meta-anaylses there are? This can be attributed to a few factors:

• Many topics do not have enough lower-level research completed to create a thorough SR
• Many topics do not lend themselves to "pure" SRs
• Requirements for SRs are stringent, causing many attempts to fall short in methodology
• High-quality SRs take a lot of TIME and effort.

The Cochrane Collaboration estimates about a year to complete the process, and this is often by teams of people working together on one review.