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Navigating the vast ocean of academic literature can feel like setting sail without a map. For those conducting systematic reviews, having a reliable search strategy based on a solid research question is akin to having a compass and chart. One of the fundamental tools in your navigational toolkit involves understanding the difference between free-text terms and thesaurus terms.
By mastering these concepts, you’ll chart a course to more effective and comprehensive literature searches and capture the most relevant references.
Imagine free text terms as the open sea of search terms. These are the words and phrases you use to search for relevant terms in the titles, abstracts, and keywords of references in a database. For example, if you’re researching diabetes, your free text terms might include “diabetes” “blood sugar” or “glucose levels”.
Free text searching casts a wide net, trawling through the title and abstract fields to capture as many relevant articles as possible.
The flexibility of free text searching is like having a multi-tool on a fishing trip. It allows you to capture synonyms, abbreviations, and spelling variations, ensuring you don’t miss out on crucial information.
Free text searching is particularly valuable for identifying emerging concepts not yet indexed in controlled vocabularies. Think of it as staying ahead of the curve by catching the latest fish in the sea before anyone else.
However, the open sea can be treacherous. Free text searching can sometimes lead to imprecise results, with your net bringing in a mix of relevant and irrelevant articles.
Variations in terminology in different contexts can also pose challenges, making it harder to find exactly what you’re looking for without getting bogged down by unrelated content.
Indexed terms are the buoys and markers that guide your search through the choppy waters of academic databases. These standardized subject headings, such as MeSH (Medical Subject Headings) in PubMed or the Emtree thesaurus in Embase, are assigned to articles by database indexers.
Controlled vocabularies and subject headings provide a structured way to navigate your research.
Thesaurus terms help you overcome variations in terminology, ensuring that whether you search for “heart attack” or “myocardial infarction,” you get consistent and focused results.
The hierarchical structure of thesauri allows you to “explode” broader terms to include narrower terms, improving the precision of your search. This consistency saves time and makes your search more efficient, guiding you to the richest fishing grounds.
Even the best maps have their limitations.
Controlled vocabulary terms can sometimes lag behind new developments, meaning recently published articles might not yet be indexed. They may also exclude emerging or locally used terms, limiting your catch to well-charted waters.
For a truly comprehensive catch, you need both a wide net and a precise map. Combining free text and thesaurus terms ensures you cover all bases, capturing articles that may not yet be indexed while safeguarding against various terminologies.
This dual approach provides both the breadth and depth needed for a robust literature search.
Developing a search strategy is like preparing for an epic fishing expedition.
Start by creating a concept table listing thesaurus terms and free text synonyms for each key concept. Use truncation and wildcards to capture variations of free text terms. For instance, searching for “child*” will retrieve “child” “children” “childhood,” etc.
Incorporate proximity search techniques to enhance precision and number of results. Here’s an example of a search strategy combining both approaches:
Using Medical Subject Headings (MeSH) in PubMed can significantly refine your search. For example, searching for “Diabetes Mellitus” [MeSH] ensures that all articles indexed with this specific term are retrieved, offering precision. Moreover, adding the field tag [tiab] to the ends of free-text terms ensures we are narrowing our search to the title, abstract and author keywords: diabet*[tiab] OR “blood sugar*”[tiab] OR “glucose level*”[tiab]
Search block: “Diabetes Mellitus”[MeSH] OR diabet*[tiab] OR “blood sugar*”[tiab] OR “glucose level*”[tiab]
The Emtree thesaurus in Embase is particularly useful for biomedical literature. Combining Emtree terms with free text searches broadens your net while maintaining focus. For example, using ‘diabetes mellitus’/exp along with free text terms captures a comprehensive set of relevant articles: (diabet* OR “blood sugar*” OR “glucose level*”):ti,ab,kw
Search block: ‘diabetes mellitus’/exp OR (diabet* OR “blood sugar*” OR “glucose level*”):ti,ab,kw
Many databases have different search strategies.
Web of Science relies heavily on free text searching, making it essential to include various synonyms and spelling variations. PsycINFO offers controlled vocabularies specific to psychology, while Google Scholar’s strength lies in its wide-ranging keyword searches.
Developing a search strategy is an iterative process. Start broad, then refine your search based on initial results. Consulting with information specialists or librarians can provide valuable insights and enhance your strategy.
Advanced techniques like phrase searching and adjacency searching (e.g., “diabetes adj3 management”) can increase precision. Truncation and wildcards capture variations, ensuring no relevant articles slip through the net.
However, using these techniques is dependent on the database you are searching and some databases may have better advanced technique possibilities than others.
Organizing your search results is crucial.
Use tools like citation managers to keep track of retrieved articles. Documenting your search strategies ensures reproducibility and transparency, essential for systematic reviews.
Understanding and effectively using free text terms and thesaurus terms is crucial for navigating the vast ocean of academic literature.
Combining both approaches in your search strategies provides comprehensive and precise results, essential for systematic reviews. As you embark on your next literature search, remember to use both your wide net and your precise map, ensuring no relevant article is left unfished.
Happy sailing!
Consider joining our course: “Complete Guide to Database Searching for Systematic Reviews“.
