To ensure you get meaningful and relevant search results you need to have a search strategy. Research databases don't understand the details of your search topic, so you'll need to prepare a strategy to make sure that you identify all the relevant information on your topic. Having a strategy will also help you recall a manageable number of relevant search results.
Planning a search strategy is a three step process:
Once you have used the PICO framework to identify your main search concepts, you'll need to identify keywords for each of the concepts. As part of this step, you should consider synonyms and alternative terms to ensure you don't miss vital research papers.
Think carefully about suitable keywords and synonyms (alternative words that have a similar meaning) that will enable you to find manageable amounts of relevant material - not so many results that they are unmanageable and cause information overload, or so few that you retrieve insufficient information for your needs.
For example: If you are searching for evidence on breast cancer, you should also use alternative terms as keywords such as breast neoplasm.
You may find it helpful to map out your keywords and synonyms using a table or list.
When you are searching the global literature think about differences in spellings and terminology, and incorporate alternatives into your search strategy.
For example: tumour (British spelling) vs. tumor (American English spelling)
Have acronyms or abbreviations been used in the sources you have read?
These can be included in your search terms in order to find matching results.
For example: magnetic resonance imaging and/or MRI
If you are searching across long time periods, remember that terminology changes over time. New words appear, others change meaning so be prepared to reflect this in your search strategy.
For example: tweet or twitter has a dual meaning:
Once you have identified your keywords, there are some useful techniques you should know to help you search most effectively.
It is possible to use a number of different keywords or search terms in a single search, by using operators. Operators link your search terms and define the relationship between them.
This enables more accurate searching and therefore more relevant results being returned. It also saves you time as you don't have to carry out numerous similar searches where just one or two search terms are changed each time.
The three most commonly used operators are AND, OR, NOT. These are known as Boolean operators. They can be used to broaden or narrow a search and to exclude unwanted search terms and concepts.
Use AND to narrow your search.
Using AND between your search terms narrows your search as it instructs the database that all your search terms must appear (in any order).
For example:
Breast cancer AND axillary ultrasound
Axilla AND ultrasound
- will only return results where both words are present
Because all search terms must be present, using AND makes the search more focused. In some (but not all) databases and search engines the AND is implied so if you enter multiple words the database will search for results which contain all/both words.
Use OR to broaden your search.
Using OR between search terms broadens your results as any or all of your search terms can be present.
For example:
neoplasm or tumour or tumor
Magnetic Resonance Imaging OR MRI
- will return results where either one or both of these words are present
It is extremely useful for finding synonyms or related concepts. Using OR enables you to carry out a number of similar searches in one go, saving you time.
You can use search techniques to help improve your searching. By applying these techniques, you can increase, reduce or improve the relevancy of your search results, making it easier to access to the right materials. For more, see the Search tips guide.
Truncation is a technique that broadens your search to include various word endings and spellings. This saves you time and means you don't need to enter several different search terms with the same root.
To use truncation, enter the root of a word and put the truncation symbol at the end.
The database will return results that include any ending of that root word.
Tip: The asterisk * symbol is most commonly used for truncation. However, check out the help guide in the database you are using as !, ?, or # may also be used.
For example:
child* will find child, children, childlike, childhood etc.
Radiograh* will find radiography, radiographer, radiographers, radiographic etc.
Use it with care to avoid finding too many alternatives.
Wildcards are similar to truncation but they are used to substitute for a single letter or no letter in a word.
They broaden your search by including variant word spellings.
The question mark symbol is most commonly used. However, check out the help information on the database you are using as ! , *, or # may also be used.
For example:
wom?n will find woman and women
optimi?ation will find optimisation and optimization
model?ing will find modeling and modelling
Phrase searching is the most limiting technique as it is used to specify that your terms must appear next to each other, and in the order you specify.
Phrase searching is commonly achieved by surrounding your phrase with quotation marks.
Always check the Database Help screens, as some databases may use different symbols.
Phrase searching examples:
"Magnetic resonance imaging"
"evidence based practice"
Using a combination of keyword and subject heading terms in your search strategy can be an effective way of ensuring that your search retrieves a greater number of relevant results. Indexers allocate subject headings to studies which allow you to search at subject level rather than just keyword level. This way of searching can be helpful as different authors may use different terminology for the same concepts and these references may be missed from your keyword searches alone.
In Medline, subject headings are called MeSH headings. The demonstration below shows how to run a search using subject headings on the Ovid platfrom (Medline, APA PsycInfo, EMBASE) in the 'Advanced search' mode.
Using an operator such as ADJn to define the proximity between your keywords can be helpful in increasing the precision of your results compared with using AND to combine the keywords. The ADJ operator is available on Ovid databases, but other resources have similar functions.
By itself the ADJ operator will lead to the same result as using inverted commas (it will find two words immediately next to each other). You can define the number of words between your keywords (between 1-99) to allow for greater flexibility.
e.g. gestational adj3 diabetes (returns results with the keywords "gestational" and "diabetes" within three words of each other in either direction.
Using the ADJn operator can be helpful when you are not sure of the exact terminology that may be used in the literature.
Tip - check the help section of the database you are using as these operators differ across different databases.