Searching using free text

Searching using Subject Headings in Medline is the most efficient and accurate method.  However indexing is a manual process and can take a little time. This means that the most recent papers in Medline will not yet have had Subject Headings assigned to them

To find the most recent papers you will need to use a free text search

Free text searching is less precise and will retrieve larger numbers of irrelevant papers

The most important thing to consider when using free text searching is that you now need to use all possible alternative synonyms for a term, also considering English/USA spellings.

• Let us think about how many variant terms there might be for people over the age of 65?

Searching with OR

We previously looked at searching using the AND connector which joins multiple concepts

When searching for synonyms of the same concept we use the OR connector.  

This time instead of looking for papers containing ALL of our concepts, we are now looking for papers containing ANY of our concepts.

Truncations

Truncation symbols tell the database to finish a word for you.  They are usually an asterisk *

So for example if you enter elder* into Medline the words - elder, elders and elderly will all be searched for.

Free text searching in Medline

• First untick the 'Map Term to Subject Heading' box

Synonyms are entered into the Medline search box in one long string eg:

older people OR older person OR older men OR older women OR elder* OR senior* OR retiree*

• Repeat this process for all 3 of our concepts as we did previously

• Then as we did before, we will need to join these 3 concepts together using the AND connector

You can immediately see the difference in the sensitivity of the free text searching.  When we searched this same topic using Subject Headings (MeSH) we retrieved 276 papers. This search however retrieved 1474 results

As we are only using this free text search to find the most recent papers (those that aren't yet indexed), we can now limit these results by date

• Select the previous year in the Publication Year box and then click Search

Other databases

PsycInfo and Embase are on the same platform as Medline - Ovid.  To search these databases your can follow the same method presented here.  However it is very important to note that every database has its own list of Subject Headings and they are not interchangeable!  You will need to search for the new Subject Headings each time you change databases.

• If you would like to see how to conduct this search in PubMed or Google Scholar please follow this link