To try to ensure your strategy is retrieving all the relevant studies you can create a test set of records. This is a group of records you would want (and expect) your search strategy to retrieve. This set is usually decided by the reviewers or from the studies included in an earlier review.
Before you start you MUST carefully consider what words you need to include in your search. Think about...
Your search is likely to be complex and involve multiple steps. Look at the appendices of existing reviews for an idea of what's involved in creating a comprehensive search.
You will need to adapt your strategy for each database depending on the searching options available on each one.
The techniques described below will help ensure you cover everything. Contact your Academic Liaison Librarian if you would like guidance on constructing your search.
Although databases have developed, and some will automatically search for variant spellings, mostly they will just search for the exact letters you type in. Use wildcard and truncation symbols to take control of your search and include variations to widen your search and ensure you don't miss something relevant.
A truncation symbol (*) retrieves any number of letters - useful to find different word endings based on the root of a word
africa* will find africa, african, africans, africaans
agricultur* will find agriculture, agricultural, agriculturalist
A wildcard symbol (?) replaces a single letter. It's useful for retrieving alternate spelling spellings (i.e. British vs. American English) and simple plurals
wom?n will find woman or women
behavio?r will find behaviour or behavior
Hint: Not all databases use the ? and * symbols, so check the online help screens before you start.
Watch our video on literature searching tips and tricks
Jump to 01:45 for truncation and 05:46 for wildcards.
Search operators (also called Boolean operators) allow you to include multiple words and concepts in your searches. This means you can search for all of your terms at once rather than carrying out multiple searches for each concept.
There are three main operators:
Watch our video on literature searching tips and tricks
This video covers a variety of techniques for creating a comprehensive search including using 'AND' and 'OR' to build a search statement.
Using OR will bring you back records containing either of your search terms. It will return items that include both terms, but will also return items that contain only one of the terms.
This will give you a broader range of results.
OR can be used to link together synonyms. These are then placed in brackets to show that they are all the same concept.
women AND AfricaUsing AND will find items that contain both of your search terms, giving you a more specific set of results.
If you're getting too many results, using AND can be a good way to narrow your search.
women NOT AfricaUsing NOT will find articles containing a particular term, but will exclude articles containing your second term.
Use this with caution - by excluding results you might miss out on key resources.
Sometimes your search may contain common words (i.e. development, communication) which will retrieve too many irrelevant records, even when using an AND search. On many databases, including Google, to look for a specific phrase, use inverted commas:
Your search will only bring back items containing these exact phrases.
Some databases automatically perform a phrase search if you do not use any search operators. For example, "agriculture africa" is not a phrase used in English so you may not find any items on the subject. Use AND in between your search words to avoid this.
On Scopus to search for an exact phrase use { } e.g. {agricultural development}. Using quotes on Scopus will find your words in the same field (e.g. title) but not necessarily next to one another.
Some databases use proximity operators, which are a more advanced search function. You can use these to tell the database how close one word must be to another and, in some cases, in what order. This makes a search more specific and excludes irrelevant records.
For instance, if you were searching for references about women in Africa, you might retrieve irrelevant records for items about women published in Africa. Performing a proximity search will only retrieve the two words in the same sentence, making your search more accurate.
Each database has its own way of proximity searching, so it's important to check the online help before you start. Here are some examples of the variety of possible searches:
Methodological search filters are search terms or strategies that identify a topic or aspect. They are predefined, tried and tested filters which can be applied to a search.
Examples:
Study types: 'systematic reviews', 'RCT' (randomised control trials)
Age groups: 'children', 'elderly'
They are available to select via the results filters displayed alongside your results. For instance, on PubMed after running your results it is possible to limit by 'Ages' which gives predefined groupings such as 'Infant: birth-23 months'.
Each database is unique and has its own features and tools. If you are using truncation, wildcards and phrase searching you might need to adapt your search to ensure it works correctly on each database. For instance Web of Science uses quotation marks around phrases whereas Scopus uses these brackets { }. Filtering options will also vary.
This is an example of a search and how it would be adapted for three databases (Web of Science, Scopus and PubMed)
Look at the help screens on the database you are using to work out the best strategy. Keep a record of the searches you run on each database to help you develop your search and to include in your write up. If you are doing a systematic review for publication your strategies need to be clearly and accurately recorded so that someone else could reproduce them.
Your Academic Liaison Librarian can also help you adjust your search.
Most health-related systematic reviews will involve a search on PubMed. But do you know how to create the most effective search strategy to take advantage of the Medical Subject Headings (MeSH)? This video created by John Hopkins University explains all the steps involved in ensuring your search is as comprehensive as possible.