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Clinical Essentials: Search

Overview

Discover how to systematically and effectively search health research literature.

🔍 Let’s begin your search for the information you need! 🚀


Identify Your Search Strategy

Before you begin, take a moment to explore your search options. Doing so helps you choose the best approach for your research.

Know Your Literature Search Types

  • General Search
    Quickly find research evidence for literature reviews.
  • Systematic Search
    Conduct a thorough and precise search suited for systematic reviews.

You will find detailed instructions for each search type in this guide.


1. Define Your Question

Start by crafting a clear research question using the PICO framework.

PICO Framework

  • Patient/Problem: Who is the patient, or what is the problem you're addressing?
  • Intervention: What treatment, exposure, or test are you considering?
  • Comparison: Are there any alternative interventions to compare with?
  • Outcome: What outcome are you aiming to achieve?

Example PICO Elements

  • Patient/Problem: Individuals who have experienced a heart attack
  • Intervention: Aspirin therapy
  • Comparison: Clopidogrel
  • Outcome: Prevention of subsequent heart attacks

Formulated Question

In individuals who have experienced a heart attack, is aspirin more effective than clopidogrel in preventing subsequent heart attacks?


Tips for Defining Your Question

  • Use a Template: A question template can guide you in crafting your question using PICO elements.
  • Consider Alternatives: If PICO doesn’t suit your needs, explore other frameworks like those from Maryland or Munn et al.

2. Identify Key Concepts

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.

Example Key Concepts

For our search, we'll focus on:

  • Problem: Heart attack
  • Intervention: Aspirin

3. Gather Search Terms

List the specific terms you'll use in the search box for each key concept. Consider two types:

Types of Search Terms

  • Keywords: Use words or phrases likely to appear in the information you need.
  • Controlled Vocabulary: Use standardized terms that databases use to describe and organize information. Think of them like hashtags on social media – they summarize topics and direct you to relevant content when selected.

Note: Controlled vocabulary is essential for systematic searches but optional for general searches, which can rely primarily on keywords.

Gathering 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.

Word Variations
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
Related Terms
Category Examples
Closely linked ideas cancer, malignancy, tumor
Umbrella and specific concepts cardiovascular disease – arrhythmia
Complementary ideas allergy ~ asthma

Gathering Controlled Vocabulary

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:

Approach 1
Identify Terms in Database Records

  1. Search for your topic in the article database.
  2. Choose a relevant article from the results.
  3. Review the assigned controlled vocabulary terms.
  4. Pick the term that best matches your topic.

Example of Controlled Vocabulary Terms

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.

MeSH terms in PubMed

Approach 2
Search the Controlled Vocabulary Database

To find the correct term, search the controlled vocabulary database.

Use the table below to identify the specific controlled vocabulary for each database.

Controlled Vocabulary by 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.

Example of Searching Controlled Vocabulary Databases:

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:

Example Search Terms

Concept Keywords MeSH
heart attack cardiac infarction
myocardial infarction
myocardial infarction
aspirin acetylsalicylic acid aspirin

4. Compose the Search Statement

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.

Understanding Boolean Operators

We use Boolean operators to refine the search logic.


OR Operator

Finds items containing any of your search terms.

  • Example:
    aspirin OR ibuprofen will return results that include either drug or both.

Venn diagram of OR operator


AND Operator

Finds items containing all your search terms.

  • Example:
    aspirin OR ibuprofen will return results that include both drugs together.

Venn diagram of AND operator


Parentheses (   )

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.

  • Example:
    (aspirin OR ibuprofen) AND (pain OR fever) will return results that include either drug and either condition.

Venn diagram of parentheses operator

Use the general search statement to efficiently find research evidence for your literature reviews.

Follow this formula to create your search statement:

General Search Statement Formula

(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.

Example: General Search Statement

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:

Systematic Search Statement Formula

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])

  • This formula guides the search engine to find items that include terms from both key concepts, ensuring more comprehensive results.
  • The search field tags [tiab] and [mh] enable precise targeting within the Title/Abstract and MeSH sections of PubMed records.
  • Note: This formula is designed for PubMed. If you're using other databases, you may need to adjust the syntax to align with their specific search rules.

Example: Systematic Search Statement for PubMed

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.

Refine Your Search Statement with These Techniques

Enhance the precision and relevance of your search results with these methods.

Phrase Search

To find an exact sequence of words, enclose your phrase in double quotes.


Example:
"heart attack"

Proximity Search

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.

Field Search

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:

  • Title: [ti]
  • Title/Abstract: [tiab]
  • Author: [au]
  • MeSH Terms: [mh]

Example:
In PubMed, add the search field tag at the end of your term, like this:
"myocardial infarction"[tiab]

Wildcard Search

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:

  • End of a word (truncation): neuro* (retrieves neuron, neurology, and more)
  • Middle of a word: onco*logy (retrieves oncology, oncoimmunology, and more)
  • Multiple wildcards: "vaccin* schedul*" (retrieves vaccine schedule, vaccination scheduling, and more)

Notes:

  • The examples provided are specific to PubMed.
  • In PubMed, the wildcard must follow at least 4 characters (e.g., colo*).
  • Wildcard searches may return unrelated words. If this happens, search for each variant manually.

5. Search Databases

Different databases offer specialized coverage, so choose the ones that best fit your topic.

Explore these databases for a wide range of medical research.

Databases for Health Research Literature

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.

Example PubMed Searches

For our example search on heart attacks and aspirin, take a look at the following search statements run in PubMed:

Translate Search Statements for Use in Other Databases

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.

6. Refine Your Search

Refining your search is an iterative process, where you fine-tune your approach to capture the most relevant information.

Follow these steps:

  • 1. Run a trial search
    Start with your draft search statement.
  • 2. Evaluate your results
    Assess how well the results address your research question.
  • 3. Adjust your search
    Refine your search terms and techniques to get more relevant results.
  • 4. Repeat the process
    Continue refining until you're satisfied with the results.

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:

  • You’ve refined your search multiple times and are not uncovering new information.
  • Your search results include studies that appear in the reference lists of key articles.
  • Experts have reviewed your search strategy and do not have any further suggestions.

While searching the literature, you might run into some common challenges. Here’s how to handle them:

Addressing Common Challenges

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

How to Narrow Your Search Criteria

If you’re getting a lot of irrelevant search results, try these strategies to narrow your focus and find more specific studies:

Techniques to Narrow Your Search
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.

How to Expand Your Search Criteria

If you’re getting limited search results, try these strategies to expand your search and include a wider range of studies:

Techniques to Expand Your Search
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.