For an extensive literature or systematic search, it is necessary to prepare your search well. The first step is to set up your research plan. More about building a search strategy see the LibGuides: Search Strategy and Clinical Questions.
For a systematic search, it is useful to build your search in a document, but also to create an NCBI account in PubMed so that you can save your search and update it later.
We use PubMed's "Advanced Search Builder" for systematic searches. You can get here by clicking "Advanced" under the search box.
(Click image to enlarge)
In PubMed you can truncate using the wildcard: *. Truncation means that you also search for all possible endings after your search term. For example, at minor* you search for minor, but also minority and minors.
You can see which search terms or letters PubMed pastes after your term after using this wildcard by clicking on: 'Show index' in the Advanced Search Builder, You can also see how often these search terms occur in the database. Above you see an example for 'sleep'.
Note: Truncation can produce irrelevant results. So think carefully whether and where it is useful. Read more in the helpfiles of PubMed.
When searching PubMed you can search on various 'fields' such as author or title of an article.
In the systematic search you are generally interested in the fields: title, summary, keywords of the author and also MeSH. Searching by title, summary and author keywords can be done in PubMed by searching for 'Title/Abstract'.
MeSH (Medical Subject Headings) are standardized keywords that refer to the content of an article.
Search on MeSH to find the many references without abstract and/or somewhat cryptic titles. Use the expertise of indexers from NLM who assess the content of the articles. In addition, you search for Title and Abstract to find the newest - not yet MeSH provided- references.
More about MeSH here.
It is best to build your search per element in the 'Query Box'. In the image above you see the Query box. Click image to enlarge.
You can enter any search term in the top 'Add terms to the query box'. To the left of this you choose in which field you want to search (for example MeSH, but see the note below, or Title/Abstract). Add your search term to the 'Query box' by clicking on 'ADD' on the right. Choose AND, OR or NOT, or type/paste your search terms directly into the 'Query box'. Type [MH] to search for the MeSH (but see the note below) and [Tiab] to search the Title and Abstract fields.
You can find more field codes here.
Connect the search terms within an element with OR. Perform a search of your element in the query box by clicking 'Add to History' next to the 'Search' button on the right-hand side of the query box.
* Note: first look up the correct MeSH term in the MeSH database!
Check in the History and Search details (see image left) which elements broaden (many results) and which elements narrow your results (few results). Adjust your search accordingly.
Connecting elements can be done in two ways:
1) Next to the search of each element, click on the three dots under 'Actions' and choose 'Add Query'. ’.
2) Connect your search within the 'Query Box' and type for instance #6 AND #7 to connect these searches.
You can expand your search by clicking on the red framed symbol (see image). Here you can see how PubMed translated your search and what was actually searched for.
You see an example in the image on the right. Click on the image to enlarge it.