Systematic Reviews (2+ people)

Search strategy is an umbrella term which can be used to describe the overarching process which runs from the initial, preparing to search stage all the way up to the applying limits stage.

This could include:

• Identifying initial terms from your question
• Searching for / recording synonyms for those terms
• Deciding which databases you want to search, selecting an appropriate number for your literature review which index journals relevant to your research area. Don't just put the names of databases into your protocol because other people have done that. Check whether (a) their coverage is relevant to your research topic, and (b) that we subscribe to that database
• For databases which have inbuilt thesauri, decide whether you want to search using any of their controlled vocabulary 

Remember! Searching for controlled vocabulary is something that you do in addition to searching for the free-text keywords you've identified from your research question, articles you've already read, terminology you've come across in practice

• Choosing what (if any) wildcards and search tools to use - taking into account the requirements of different databases
• Creating your search string - this is necessary to ensure that you give the database the correct information on how to combine your terms with Boolean Operators. When you come to do the actual searching, for a systematic review, you would generally look for each individual term separately and then combine them together, but recording your search string with the Boolean Operators in place can help with accuracy
• Deciding which limits you want to apply - these are also known as inclusion / exclusion criteria. Some limits you'll be able to apply directly from the options given by each database. Some limits will be present in one database but not another; some options may seem helpful but there could be issues if you use them e.g., limiting by study type, limiting by geography and so on

• Limiting by date - you can use whatever date range you want as long as you can justify it. Don't just pull the dates out of thin air, if you were challenged as to why you chose that date range, could you justify that choice? If someone has already done a systematic review of the literature on your topic (e.g., 2005 - 2015) then you could justifiable run your systematic review from 2015 / 2016 to the present day. If you're doing research on the use of a particular piece of equipment, software, intervention and it was only created / released / brought into practice in 2017 then it would be reasonable to start your research from that date.

• Limiting by language - this isn't something that is generally recommended. Research in a specific area may be concentrated in non-Anglophone countries or journals if researchers / practitioners in those countries identified a need or secured funding first. Excluding non-English articles from the get-go also introduces language / geographic bias - that research exists - so even if you can't read it, or get it translated, you still need to acknowledge that that research exists on your topic, and that you found it. In this way, subsequent researchers who may be able to translate those articles will be able to see from your research that you did not miss those papers and this gives further weight to your systematic review's level of robustness.

Databases will generally provide article titles and abstracts translated into English so that researchers have awareness of the article's content, so you will see those articles which are relevant to your topic.

• Limiting by geography - despite appearances, where databases have a geography limit option it is rarely related to where the research was conducted and more likely to be referring to either where the journal is published, or the geographic area that the author(s) are affiliated with. If geography is an important factor in your research - perhaps your research involves guidelines or regulations from UK-based professional or regulatory bodies - then you would be better off doing one of the following:
  • Identify the range of geographic terms relevant to your research. The obvious ones would be for country names, so for the UK you could consider, England, Wales, Scotland, Northern Ireland, United Kingdom, and Great Britain. However, there are a couple of issues with this as some authors may mention narrower geographic locations, so cities rather than countries: London, Birmingham, Glasgow, Northampton so if you just search for country-level geographic terms you could miss results. There's also the potential for authors to not mention any geographic terms at all in the main search areas e.g., abstract and article title, so again you could miss relevant material.
  • The other option would be to avoid making any geographic limitations at all when you're conducting your search(es). Once you have your results (after screening and removing duplicates) you can then scan through those papers to see if you can identify where the research was conducted. 

This would be the preferred option unless you were looking for country-specific or professional body regulations / guidelines research.

• Limiting by population characteristics - this could be age or gender and, in some databases, you may get the option for limiting by whether they're an inpatient / outpatient. But for many of these limits it would probably be better to search for those characteristics as part of your search strings, and not use the limit options in the database's sidebar

• Limiting by study type - most databases don't offer this limit option and, where it is offered, articles are classified by AI not by a human assessing the article's information. For this reason, if you are wanting to limit your results by study type, you could instead search for the study type, and for terms used to describe how that study type's data can be gathered, as part of your overall search strings as this should be a more effective way of locating relevant articles

• Decide what (if any) reference management tool you're going to use - for a systematic review (really for any literature review) it's strongly recommended that you use a reference management tool to organise your results, screen articles and help with removing duplicates, and finding full-text. You can also use it to when you come to the part of the process where you read the full-text of the articles as most reference managers have an in-built PDF reader so, once you've attached the PDF of the article to the reference, you can then read the full-text in the reference manager, make notes / highlight, and then decide if it's suitable to be included

• Set up your PRISMA flow diagram - make sure you're using the correct PRISMA diagram for the type of systematic review you're planning to do. There are also a number of extensions that have been developed to help with reporting different aspects of systematic reviews so you may want to have a look at those and decide whether or not you need / want to use any of them. You can also access a checklist on the PRISMA website which covers the different parts of a systematic review