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In-depth searching


The basic steps for in-depth searching are the same as for rapid searching, however extra time and effort are put into certain steps, such as gathering synonyms, adding subject headings, such as MeSH terms for PubMed, and searching more than one database.

Identify a topic

Ensure you have a clear idea of what you're looking for, to avoid wasting time by searching vaguely.

Use PICOT to identify main concepts

Write a question to represent what you want to find out about at this point in your work. You are likely to have different questions at different stages of your work. Use the search building steps below for each question.

If the question is not clinical, the PICOT model may not apply. In that case, simply identify the main concepts.

Select the initial keywords

Start with the 2 or 3 most essential PICOT terms, and add others in if you need to, e.g. if the search results are not specific enough.

Collect alternative keywords

To increase the chance of finding all papers, include alternative keywords to account for the fact that authors may use different terminology to describe the same concept. For in-depth searching, you will put more time and effort into identifying synonyms, as you are searching more thoroughly for papers that may be harder to find.

To find synonyms:

  • Do some quick searching in key databases, and check any relevant papers.
  • Check the 'entry terms' of relevant MeSH headings.
  • Think of any alternative spellings or acronyms.
  • Consider more specific terms, for example, for NSAIDs, you could also include aspirin or ibuprofen.
  • Search the internet. Wikipedia often lists synonyms, and you could do a quick web search for synonyms.

Add subject headings

For each search word, determine if there's a standardised subject heading to include in your search (this is an essential part of systematic literature reviews, and best practice for thorough literature searching).
To find MeSH terms for a PubMed search:

  1. Open PubMed.
  2. Select the MeSH database, found under the 'Explore' menu at the lower right of PubMed's homepage.
  3. Search for the first concept you are interested in, e.g. bladder. 
  4. Related MeSH terms will be provided – tick the box to select the term you want to use or open the record to see more detailed options.
  5. Click 'Add to search builder'.
  6. Copy the MeSH term, e.g. "Urothelium"[Mesh] into your search.
  7. Repeat steps 3 - 6 for each concept/keyword.

Subject headings for other databases

Other databases have subject heading systems that work similarly, e.g. Ovid Medline also uses MeSH terms, Embase uses the Emtree system and CINAHL uses CINAHL headings.

Including subject headings in other databases is recommended if you are conducting a systematic review search. For a narrative literature review search, including MeSH terms for the PubMed search is a good idea. To search other databases, remove the MeSH terms. The other parts of your search string, including the keywords, Boolean operators, truncations and phrases will work in any database. Removing the MeSH terms from the search strategy allows the search to be run in any other database.

For assistance with subject headings please contact an HSM faculty librarian.

Simplify the keywords

Use the truncation wildcard, (the asterisk symbol *) to retrieve alternative word endings by placing the asterisk at the end of the root of the word, e.g. child* will allow the database to return results that have the words child, children or childhood.

Enclose the keywords in quotation marks e.g. 'overactive bladder syndrome', to return results where the keywords appear next to each other and in the same order,

Combine the keywords with Boolean logic

Combine concepts by using the Boolean operator AND, e.g. "deep vein thrombosis" AND diagnos* AND d-dimer

Join keywords that represent the same concept together with the Boolean operator OR, and enclose them in round brackets, e.g. (fish oil* OR "omega 3")

Here is an example search strategy with multiple concepts, where each concept includes more than one keyword.

Example topic:

The effect of testosterone on bladder function.

Example search strategy:

(bladder OR "Urinary Bladder"[Mesh] OR urothelium OR "Urothelium"[Mesh])
(testosterone OR "Testosterone"[Mesh])
(effects OR bladder contractility OR mediator release OR acetylcholine OR "Acetylcholine"[Mesh] OR ACh OR adenosine triphosphate OR ATP OR "Adenosine Triphosphate"[Mesh] OR prostaglandins OR "Prostaglandins"[Mesh] OR overactive bladder syndrome OR OAB)

Once you've added ANDs ORs and brackets, copy and paste your search into PubMed and start searching.

Test the search strategy

After creating the initial PubMed search, test it, then modify and improve it. Add new, useful keywords to the search string and search again. Remove words that don't help.

You need to feel confident that you are finding all papers relevant to your current purpose.

Where to search

When searching for all information on a topic, it is typically carried out in the 'studies' layer of the pyramid. Studies are usually published as journal articles.

PubMed is a great initial database to search. Other key databases for many topics include Embase and CINAHL. Check the journal articles tab within this guide for links to these and other additional databases.

Download the in-depth guide and search builder template

Nutrition and dietetics