Literature and Systematic Reviews for Public Health

Searching for literature for a systematic or scoping review is a different process than searching for a different type of literature review. For a generic literature review, you may try searching a lot of different ways with different combinations of keywords, and then choose literature from each set of search results you get in a database or grey literature source. By contrast, in a systematic review your goal is to find all relevant articles with one well-built, reproducible search strategy that you'll translate for all databases you intend to search. Instead of cherry-picking articles from the results you get, you'll screen all of the articles you find for their relevancy to your project. More information about the systematic review process can be found in the Review Methodology section.

In this section, we'll explore how to build a search strategy to capture all relevant articles. Be sure to read the Searching Databases section of this guide first, as the information in this section will build upon the information in that section.

Build your search strategy first in PubMed, as this is the premiere source for biomedical information and a comprehensive database. Then, you'll translate your search for use in other databases; but you will be using the same search strategy for all databases. This is part of what makes the search strategy reproducible, which is a vital component of minimizing bias in your review.

This video on Advanced PubMed Searching covers the below steps (with a different example question):

Start with a specific, well-built research question. Using a question framework like PICO or PEO makes the next steps easier!

Let's use this example research question: How does access to water impact food insecurity for the population of East Africa?

Just as we did in the Searching Databases section, break your question down into its component parts:

1. access to water
2. food insecurity
3. East Africa

Start brainstorming keywords and synonyms to describe each of your concepts. Try to think of how authors might describe each concept. Authors might say access to water, or they might say water access or clean drinking water instead. Sometimes the inverse of a term can also be useful; if you want articles on food insecurity, you might try food security as well. If you are looking for literature about a geographical area, be specific. A database will not understand that East Africa includes Kenya and Rwanda; you'll need to specify each country.

MeSH terms (Medical Subject Headings) are indexing terms, or standardized keywords, which are attached to many articles in PubMed. It is good practice to include MeSH terms as well as keywords in any systematic or scoping review search strategy.

To find the most relevant MeSH terms for your topics, navigate to the PubMed homepage and click on "MeSH Database" underneath "Explore," which is under the search bar.

In the MeSH database, search for your first concept. In this example, I searched for access to water, and the following options came up:

"Water Insecurity" seems to be the most relevant to me, so I'll click on that to view the MeSH database entry for this term. I'll review the definition of the term, and when I decide it's the term I want to use, I'll click "Add to Search Builder."

This will give me the MeSH term with the correct field code (the text within the brackets at the end of the word) to paste into my search. I'll copy and paste this and add it to my list of brainstormed keywords.

Repeat this for each concept. Sometimes, you may want to use more than one MeSH term.

Searching for a MeSH term will search for all of the terms underneath it in the hierarchy. For example, searching for "Africa, Eastern"[Mesh] will also find the following MeSH terms, which means you only need to include "Africa, Eastern"[Mesh] to find all of them.

Add all of your MeSH terms to your list of keywords.

Field tags are bits of code to tell PubMed to only search for the keyword you've entered in certain places. By default, PubMed searches in "All Fields," which includes the title, abstract, journal title, author names, and author affiliations, among other fields. If you want to search for rice (the food), and you don't use a field tag, then PubMed will also find articles written by researchers at Rice University.

Using field tags is particularly helpful when you're searching for geographic locations, because you want to find articles that are about that location--not necessarily work by researchers just living or working in those areas.

The most common field tag to use is [tw], which stands for "text word," and tells PubMed to skip fields like journal titles, author affiliations, etc.

Add this field tag to the end of each of your keywords. Now is the time to add quotation marks around phrases as well.

One of the major differences between searching for a literature review and searching for a systematic review is that you will use all of the keywords you've brainstormed in one search strategy, instead of picking and choosing from each list that you brainstormed.

Take all of the keywords from one column and combine them with OR, then put parentheses around the lists.

("access to water"[tw] OR "water access"[tw] OR "drinking water"[tw] OR "clean water"[tw] OR "water treatment"[tw] OR "Water Insecurity"[MeSH])

("food insecurity"[tw] OR "food security"[tw] OR "food accessibility"[tw] OR "access to food"[tw] OR malnutrition[tw] OR "Food Insecurity"[Mesh] OR "Malnutrition"[Mesh])

("East Africa"[tw] OR Burundi[tw] OR Djibouti[tw] OR Eritrea[tw] OR Ethiopia[tw] OR Kenya[tw] OR Rwanda[tw] OR Somalia[tw] OR Sudan[tw] OR Tanzania[tw] OR Uganda[tw] OR "Africa, Eastern"[Mesh])

Now, add the word AND in between each concept.

("access to water"[tw] OR "water access"[tw] OR "drinking water"[tw] OR "clean water"[tw] OR "water treatment"[tw] OR "Water Insecurity"[MeSH])

AND

("food insecurity"[tw] OR "food security"[tw] OR "food accessibility"[tw] OR "access to food"[tw] OR malnutrition[tw] OR "Food Insecurity"[Mesh] OR "Malnutrition"[Mesh])

AND

("East Africa"[tw] OR Burundi[tw] OR Djibouti[tw] OR Eritrea[tw] OR Ethiopia[tw] OR Kenya[tw] OR Rwanda[tw] OR Somalia[tw] OR Sudan[tw] OR Tanzania[tw] OR Uganda[tw] OR "Africa, Eastern"[Mesh])

Your search strategy is now ready to be run in PubMed. Please go to the Running Your Searches page for more information on searching in PubMed and then translating your search for other databases.