There are many different ways to begin a search
Now that's we're familiar with how PubMed is set up, let's try a few different ways of searching the database. In using the query breast cancer screening, let's see what we can find by utilizing a few different search methods.
Exact Controlled Vocabulary
To begin this search, we need to find the correct MeSH term used to define "breast cancer." To search the Thesaurus, use the dropdown menu to the left of the basic search box on the PubMed homepage to select MeSH. Without entering anything into the search box, click Search. This will take us to the MeSH homepage. In the search box, type breast cancer and hit Search.
The MeSH term for breast cancer is breast neoplasms. Click on this subject heading to see how we can explode/restrict our use of it. You'll see a list of subheadings as well as the hierarchical tree where the term derives from. Under the subheadings in the main column there is the chance to Restrict to MeSH Major Topic and not include any sub terms. Make sure you click these before adding the term to the search builder (on the right hand side).
Our search retrieves quite a lot of results even with the major topic restriction.
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Word Controlled Vocabulary
breast neoplasms is plural, but say we want to find every instance of breast cancer in the database. This is where we use truncation. In the same MeSH homepage search box, type in breast neoplasm* and hit Search.
Three MeSH terms are identified, all matching our broad goal. Click the ticky boxes beside each of the three results, and on the right hand side of the page click Add to Search Builder, changing the Boolean AND to an OR in the dropdown. Because we didn't restrict to major topics or subheadings, this search will be conduc
Click Search PubMed. Our results have expanded to over 190,000 hits, finding articles we wouldn't have found using only an Exact CV search.
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Freetext
Sometimes it's useful to search using the Freetext fields. This is especially important in gathering articles and citations for items that have been added to PubMed but have not been MeSH indexed yet! For this search we'll focus on the second part of our original query: cancer screening. First let's use the same MeSH homepage to find an appropriate term in the index for cancer screening. If we type it in and press Search, we're taken directly to the early detection of cancer page.
Instead of ignoring our original search term, let's add it to the search builder, adding truncation to catch any variations of the term. Don't forget to change the Boolean AND to an OR.
Our results are a good 18,000+ hits. (In case you're wondering, had we only used early detection of cancer we would have only had 2,000 hits.)
Putting it all together
Now let's build both parts of our searches together using the Advanced Search function. Our search history is at the bottom of the page along with our search sets. Because #30 restricts the term breast neoplasms to MeSH Major Topic, we will include it to build our newest set. Our newest command should look like: ((#30) OR #31) AND #32. Press Search.
Because we haven't included any filters, listed on the left sidebar, all of our results seem to be on target. But 4,000 results is way too much for any one person to handle. Why don't we filter our results by clarifying that we're only interested in articles about humans, published between the beginning of last year to the end of this year, and only those articles where full free text is available? What do our results look like then?
Factual Field
What if we were searching for an article on breast cancer screenings from a specific Journal? We know it's the New England Journal of Medicine but we aren't sure the name of the article, just that it was recently published? This is where Factual Fields come into play. Using the Advanced Search Function, let's narrow down our search.
Using the dropdown menus to the left of the search boxes, specify the date of publication (we're going back two months, to the beginning of October - note the way dates are written), begin typing the Journal name until the autocomplete function finds the correct name, and specify our MeSH term for breast cancer, ANDing all of the boxes together. (TIP! If you were to write the field qualifications out in Command Mode, the field tags are always in [ ] brackets.)