Discover how to systematically and effectively search health research literature.
🔍 Let’s begin your search for the information you need! 🚀
Before you begin, take a moment to explore your search options. Doing so helps you choose the best approach for your research.
You will find detailed instructions for each search type in this guide.
Start by crafting a clear research question using the PICO framework.
In individuals who have experienced a heart attack, is aspirin more effective than clopidogrel in preventing subsequent heart attacks?
Tips for Defining Your Question
Choose Key Ideas: Pick two or three main ideas from your research question. Fewer concepts help you cast a wider net, leading to a more complete search.
Focus on the Problem and Intervention: These concepts are often emphasized in abstracts and use standardized terms, making them ideal search terms.
For our search, we'll focus on:
List the specific terms you'll use in the search box for each key concept. Consider two types:
Note: Controlled vocabulary is essential for systematic searches but optional for general searches, which can rely primarily on keywords.
List terms associated with each concept, including word variations and related terms.
The examples in the following tables will help you identify relevant terms.
| Category | Examples |
|---|---|
| Synonyms | hypertension, high blood pressure |
| Word forms | diabetes, diabetic |
| Plural forms | viscus, viscera |
| Acronyms | AIDS |
| Abbreviations | CO2 |
| Alternate spellings | pediatrics / paediatrics (US / UK) |
| Clinical jargon | sub-therapeutic, idiopathic |
| Slang | bounceback |
| Historical terms | dipsomania for alcoholism |
| Common spelling errors | Alzheimer, Alzheimer’s |
| Category | Examples |
|---|---|
| Closely linked ideas | cancer, malignancy, tumor |
| Umbrella and specific concepts | cardiovascular disease – arrhythmia |
| Complementary ideas | allergy ~ asthma |
When using controlled vocabulary in your searches, it's important to use the precise standardized term for your topic.
Although it is optional in general searches, controlled vocabulary is crucial for systematic searches to ensure thorough and precise results.
Here are two approaches to help you find the right term:
In the PubMed database, these terms are called Medical Subject Headings (MeSH).
You can find a section in PubMed records that lists the MeSH terms for each article.
To find the correct term, search the controlled vocabulary database.
Use the table below to identify the specific controlled vocabulary for each database.
| Database | Controlled Vocabulary |
|---|---|
| PubMed | MeSH (Medical Subject Headings) |
| Embase | Emtree |
| PsycInfo | Psychological Index Terms |
| CINAHL | CINAHL Subject Headings |
Note: Always use the specific controlled vocabulary for the database you're searching.
For a PubMed search, use the MeSH database to identify the controlled vocabulary term for your topic.
For example, searching heart attack in the MeSH database will reveal that the precise term is myocardial infarction.
For our search on heart attack and aspirin, here are the keywords and controlled vocabulary:
| Concept | Keywords | MeSH |
|---|---|---|
| heart attack | cardiac infarction myocardial infarction |
myocardial infarction |
| aspirin | acetylsalicylic acid | aspirin |
Combine your search terms using the Boolean operators OR, AND, and parentheses to clearly define the logical relationships between them.
These operators help the search engine better understand your search logic, leading to more accurate results.
We use Boolean operators to refine the search logic.
Finds items containing any of your search terms.
Finds items containing all your search terms.
Group search terms with parentheses to tell the search engine which elements to process first.
Like in math, the search engine handles the terms within parentheses first, allowing you to nest one search within another.
Use the general search statement to efficiently find research evidence for your literature reviews.
Follow this formula to create your search statement:
(Concept #1 OR Synonyms OR Related Terms) AND (Concept #2 OR Synonyms OR Related Terms)
This formula helps the search engine find results that include terms from both key concepts, ensuring more comprehensive results.
For our search on heart attack and aspirin, we use:
(heart attack OR cardiac infarction OR myocardial infarction) AND (aspirin OR acetylsalicylic acid)
Use the systematic search statement to conduct a thorough and precise search suited for systematic reviews.
Follow this formula to create your search statement:
For use exclusively in PubMed:
(Concept #1[tiab] OR Synonyms[tiab] OR Related Terms[tiab] OR Controlled Vocabulary[mh]) AND (Concept #2[tiab] OR Synonyms[tiab] OR Related Terms[tiab] OR Controlled Vocabulary[mh])
For our search on heart attack and aspirin, we use:
("heart attack*"[tiab] OR "cardiac infarct*"[tiab] OR "myocardial infarct*"[tiab] OR "myocardial infarction"[mh]) AND (aspirin[tiab] OR "acetylsalicylic acid"[tiab] OR aspirin[mh])
In literature searches, double quotes are used for precise phrase searches, while the asterisk acts as a wildcard to capture word variants.
Read more about these search refinement techniques in the next section.
Enhance the precision and relevance of your search results with these methods.
To find an exact sequence of words, enclose your phrase in double quotes.
Example:
"heart attack"
Find words that appear within a specific distance from each other.
For a PubMed search, use this format:
"search terms"[field:~N]
See more details.
Example:
"hip pain"[Title/Abstract:~2] retrieves phrases where these terms are within two words of each other, like hip pain, hip joint pain, and pain in right hip.
Direct your search to a specific section of a database record by adding a search field tag to your term.
Common PubMed Search Field Tags:
Example:
In PubMed, add the search field tag at the end of your term, like this:
"myocardial infarction"[tiab]
Find variations in the spelling or form of a word or phrase by using a wildcard character, typically an asterisk *, to replace one or more characters.
Examples:
Notes:
Different databases offer specialized coverage, so choose the ones that best fit your topic.
Explore these databases for a wide range of medical research.
| Database | Subject Coverage |
|---|---|
| PubMed | Biomedical and life sciences |
| Embase | Biomedical, life sciences, and pharmacology |
| PsycInfo | Psychology and behavioral research |
| CINAHL | Nursing and allied health |
| Web of Science | Multidisciplinary |
| Google Scholar | Multidisciplinary |
Explore additional databases in our A-Z Databases directory.
When you're ready, enter your draft search statement in the database search box.
For our example search on heart attacks and aspirin, take a look at the following search statements run in PubMed:
The example search queries provided in this guide are designed for PubMed.
If you're using other databases, you may need to adjust the PubMed search statement syntax to align with their specific search rules.
Refining your search is an iterative process, where you fine-tune your approach to capture the most relevant information.
Follow these steps:
After several rounds of search refinement, you may notice that further changes aren't significantly improving your results.
You might decide to wrap up your literature search if:
While searching the literature, you might run into some common challenges. Here’s how to handle them:
| Challenge | Strategy |
|---|---|
| Irrelevant results | Narrow your search criteria to focus on more specific studies |
| Limited results | Expand your search criteria to include a broader range of studies |
If you’re getting a lot of irrelevant search results, try these strategies to narrow your focus and find more specific studies:
| Technique | Description |
|---|---|
| Apply Database Filters | Limit results by date range, age group, article type, and more. Note: If you’re doing a systematic review, it’s best to avoid these filters. |
| Use Phrase Searches | Place exact phrases in double quotes, e.g., "kidney failure" |
| Conduct Field Searches | Target specific sections like the title, abstract, or controlled vocabulary. |
| Choose a More Specific Idea | For example, use arrhythmia instead of the broader term heart disease. |
| Add More Concepts | Incorporate additional concepts from your research question. |
| Use Search Filters | Apply pre-defined criteria to focus on specific research characteristics. |
If you’re getting limited search results, try these strategies to expand your search and include a wider range of studies:
| Technique | Description |
|---|---|
| Include More Synonyms | For example, use myocardial infarction OR heart attack |
| Explore Similar and 'Cited By' Articles | Follow these database links to find related studies. |
| Review Reference Lists | Check the reference lists of relevant articles to discover additional sources. |
| Choose a More General Idea | For example, use heart disease instead of the more specific term arrhythmia. |
| Introduce Related Concepts | Include related concepts (e.g., asthma OR allergy), to explore connected topics. |
| Search Across Multiple Databases | Use resources like PubMed, Embase, PsycInfo, CINAHL, and Web of Science. |
