Searching for Systematic Reviews & Evidence Synthesis: Recording search strategy & results and registering your protocol

PRISMA (the Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 
Updated in March 2021.
In February 2021 the PRISMA extension for searching was published. The new searching checklist includes 16 reporting items, each of which is detailed with exemplar reporting and rationale. It includes the guidance to "Include the search strategies for each database and information source, copied and pasted exactly as run"

Several extensions of the PRISMA Statement have been developed to facilitate the reporting of different types or aspects of systematic reviews. These include for Abstracts; Equity; Harms (for reviews including Harm outcomes); Individual Patient Data; Network Meta-Analyses; Protocols; Diagnostic Test Accuracy; and Scoping Reviews.

The PRISMA 2020 checklist states for '#7 Search strategy' that you should "Present the full search strategies for all databases, registers and websites, including any filters and limits used". The new 2021 PRISMA extension for searching extends this to "include the search strategies for each database and information source, copied and pasted exactly as run". These reported electronic search strategies normally appear in an appendix or as supplementary material to a published systematic review as they are too long to include in the main part of the systematic review. Some published systematic reviews only include a search strategy optimised for one database whilst others e.g. some Cochrane systematic reviews will publish the search strategies for all databases searched. It is not necessary to include the number of results for each search line (although this can be helpful if you are seeking feedback on the search strategy).

In many databases you can simply copy and paste the search strategy from the screen but you may also find that some databases allow you to download the search strategy (which may require less formatting than the copy and paste option). 

For a search strategy on the Ovid platform (Medline, Embase, APA PsycInfo, Global Health etc) take the following steps:

1. Run your search
2. Click on 'Share Search History' 
   This will expand to give you 3 options.
   

• Select 'Email All Search History' to email the details to yourself.
  or  
• Select 'Copy Search History Link' to obtain a URL which will allow you or anyone you share the link with run the search on Ovid (if they are external to King's they will need to have access to the same database via their own institution or the NHS). Paste into a Word document, email, OneNote.
  Note if you are logged in using KCL credentials and are sharing the search history link to an external colleague please edit the search strategy after you have pasted it, leaving a URL starting http://ovidsp.ovid.com... 

or

• Select 'Copy Search History Details' to copy the full search strategy. Paste into a Word document, email, OneNote etc. Paste in the URL as well for maximum research transparency and replicability.

Best practice is to publish your systematic review search strategy alongside the systematic review. As well as including this in an appendix/supplementary information on a journal site it can also be submitted to a data repository.

• The King's Research Data Management System is a a research data repository service providing long term storage and public access for datasets that support published research and/or have long term value. Search strategies fall into this category. View the Libraries & Collections Research Support webpage (Preserve > Deposit with King's tab) for more information on how to submit. Please note that this is normally limited to researcher and PhD level. 
• Other data repositories are also linked from the Libraries & Collections Research Support webpage (Preserve > Deposit your data tab)

Examples of flow diagrams from published systematic reviews (see the PRISMA Flow Diagram for a template).

You will see the information recorded can differ even in Cochrane Reviews but the flow diagram can be a useful place to summarise what databases and other resources have been searched and the reasons why full text articles which were assessed have been excluded (as recommended by PRISMA).

Example 1:

From: Kew KM, Carr R, Donovan T, Gordon M. Asthma education for school staff. Cochrane Database of Systematic Reviews 2017, Issue 4. Art. No.: CD012255. DOI: 10.1002/14651858.CD012255.pub2.

Example 2:

From: Welsh EJ, Carr R. Pulse oximeters to self monitor oxygen saturation levels as part of a personalised asthma action plan for people with asthma. Cochrane Database of Systematic Reviews 2015, Issue 9. Art. No.: CD011584. DOI: 10.1002/14651858.CD011584.pub2.

The first step of any systematic review should be to write a protocol outlining  your project and how it will be carried out. 

To avoid unplanned duplication and enable comparison of reported review methods or meet funders' or publishers' requirements, consider registering your systematic review's protocol and also searching to see whether a systematic review on your prospective topic has also been registered in order to avoid duplicating research.

Key registers are listed below.

PROSPERO includes details of any ongoing systematic review that has a health related outcome in the broadest sense. Systematic review protocols registered on PROSPERO can include studies of any design. Work is underway to facilitate the inclusion of reviews of pre-clinical studies.

If your Systematic Review does not fit PROSPERO's criteria e.g. a review of pre-clinical studies then you could consider publishing your protocol on one of the following sites:

Scoping reviews also can't currently be included on PROSPERO. The PRISMA guidance for scoping reviews (PRISMA SCr) suggests some locations for registering the protocol including:

Other registers of systematic review protocols include the Cochrane Collaboration, Campbell Collaboration and Joanna Briggs Institute. There are also some journals which publish Systematic Review protocols e.g. BioMed Central's Systematic Reviews.