LibGuides: Topic: Systematic Searching for Evidence Synthesis: Developing &amp; Documenting Your Search Strategy

How Do You Start?

Where do you begin when developing a search strategy? Start from what you know! You probably have a few articles you feel are right on target for your research question, or at least ones that are close to your area of interest. You might have literature reviews (narrative or systematic) that relate to it. All of those will yield valuable terminology, authors, references, and other information that can help you design an effective search.

You'll start with lots of exploratory searches to determine the most useful vocabulary and databases on which to focus your efforts. The more thoroughly you document your efforts, the more comprehensive and successful your final searches will be. Below are some strategies that will help you with this process.

Create a Concept Table

You'll be crafting a complex search strategy. Creating a concept table is one effective way to ensure your search is as thorough as possible. You'll use it to define the main ideas in your research question and gather terminology to use in your search.

The concept table can be downloaded either as a Word document or Excel spreadsheet. Use the one that works best for you to develop your concept table in preparation for searching.

Watch the video below to learn about how to create and use a concept table.

Using a Concept Table for Systematic Searching transcript

Keywords vs. Controlled Vocabulary

There are two major categories of language used in systematic searching, both of which are essential to an effective search.

Keywords, sometimes called free text terms, are any words you can think of related to your topic. They may include scholarly or technical language, terms unique to certain disciplines, modern or outdated terminology, or different forms of the same words (singular, plural, regional spelling differences).
Controlled vocabulary, sometimes referred to as subject headings, descriptors, or index terms, are the standardized terminology used by databases to label references based on their content. Controlled vocabulary are generally arranged in a hierarchical thesaurus that explains what the terms mean and how they are related. Many, but not all, scholarly databases have a unique controlled vocabulary. Two examples are PubMed, which uses MeSH (Medical Subject Headings), and APA PsycInfo, which uses the APA Thesaurus of Psychological Index Terms.

Because exhaustive searching means considering all the ways relevant sources may be described, systematic searches must include both keywords and controlled vocabulary.

When you begin brainstorming keywords, first identify the main ideas of your research question. Then, in your concept table, write down any word or phrase you can think of that might be used to describe each component of the question.

Lots of words may be written in different ways, such as differences in spelling, or singular and plural forms; see the Different Forms of the Same Word tab in this box for some suggestions of how to deal with that.

Watch this short video to see how you might approach this process in your concept table!

Brainstorming Keywords: Begin Building a Concept Table transcript

Consider whether there are different forms of a word that interests you. In library databases, searching for any ending of a word is called "truncation." Frequently you can use a * to truncate a word, but the symbol can vary among different databases. In some cases, you can use a "wildcard" to find alternative spellings that fall inside a word, rather than at the end.

Some examples for two popular databases are below. Different databases allow for different truncation and wildcard options. In the examples below, you'll notice that PubMed uses the * symbol for both truncation and wildcard searching, standing for zero or more characters. There must be at least four characters preceding the * either within or at the end of a word. APA PsycInfo uses * for multiple characters, # for one optional character, and ? for exactly one character.

Terms may be spelled differently depending on the researchers' language background

ischemic vs. ischaemic
- In PubMed, search isch*mic
- In APA PsycInfo, search isch#emic

Abbreviations may be useful

COPD vs. chronic obstructive pulmonary disease
- In PubMed or APA PsycInfo, search COPD OR "chronic obstructive pulmonary disease"

Singular, plural, and more

physiology vs. physiological
- In PubMed or APA PsycInfo, search physiol*
stroke vs. strokes
- In PubMed or PsycInfo, search stroke*

Some words have even more forms

anemic vs. anemia vs aenemic vs. aenemia
- In PubMed, search anemi* OR aenemi*
- In APA PsycInfo, search a#nemi*

Planning Your Search: Controlled Vocabulary

Controlled vocabulary varies from database to database. The same article may appear in PubMed, APA PsycInfo, and Embase, but be described very differently. For example, take the following article:

Attanasio, L. B., & Hardeman, R. R. (2019). Declined care and discrimination during the childbirth hospitalization. Social Science & Medicine, 232, 270–277. https://doi.org/10.1016/j.socscimed.2019.05.008

In PubMed, this is assigned several Medical Subject Headings from PubMed's controlled vocabulary, abbreviated as MeSH. This is an excerpted list: Attitude of Health Personnel; Black or African American; Delivery, Obstetric; Hospitalization; Patient Acceptance of Health Care; Pregnancy; Professional-Patient Relations; Racism

In APA PsycInfo, which uses the APA Thesaurus of Psychological Index Terms, the subject headings are: Birth; Discrimination; Hospitalization; Therapeutic Processes; Blacks

In Embase, which uses the Emtree thesaurus, some of the assigned index terms include: childbirth; ethnicity; health care personnel; hospitalization; infant; punishment; race; stereotypy

You can see that, despite some overlap in how these three databases describe the same article, there are lots of unique terms. The hierarchies from which the terms are chosen will also be different. You can use controlled vocabulary in a database to search its contents, but you can also use terms from one database as keyword in others. Looking at controlled vocabulary across several databases when building your concept table can help expand and enhance your keyword selections.

Using AND, OR, & NOT To Build a Search Strategy

There are some elements of searching that apply in any database and are essential to designing effective search strategies. If you're relatively new to database searching, or could use a refresher, scroll through the following presentation.

Using AND, OR, & NOT To Build a Search Strategy

Documenting Your Search

In any evidence synthesis project, it's vital to document the following:

Where you searched:
- This could be specific databases, but it would also include things like Google Scholar, websites, or grey literature sources.
What search strategies you used:
- You need to track exactly how you searched: the specific strategy for how you combined your search terms. The easiest way to do this is to copy the line-by-line search strategy you used in each database when you run it, as well as the full searches for anywhere else you look (such as a search engine).
How many citations you found and retained at various stages of your process, starting with your searches:
- Reporting guidelines generally require you to track how many search results you got from each place you searched, how many you had after deduplication, how many were retained at each stage of screening, and how many you ultimately included in your study.