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PubMed Search Syntax and Field Tags
Boolean Operators
PubMed supports standard Boolean operators to combine search terms:
AND
Retrieves results containing all search terms. PubMed automatically applies AND between separate concepts.
Example:
diabetes AND hypertension
OR
Retrieves results containing at least one of the search terms. Useful for synonyms or related concepts.
Example:
heart attack OR myocardial infarction
NOT
Excludes results containing the specified term. Use cautiously as it may eliminate relevant results.
Example:
cancer NOT lung
Precedence: Operations are processed left to right. Use parentheses to control evaluation order:
(heart attack OR myocardial infarction) AND treatment
Phrase Searching
Double Quotes
Enclose exact phrases in double quotes to search for terms in specific order:
"kidney allograft"
"machine learning"
"systematic review"
Field Tags
Alternative method using field tags:
kidney allograft[Title]
Wildcards
Use asterisk (*) to substitute for zero or more characters:
Rules:
- Minimum 4 characters before first wildcard
- Matches word variations and plurals
Examples:
vaccin* → matches vaccine, vaccination, vaccines, vaccinate
pediatr* → matches pediatric, pediatrics, pediatrician
colo*r → matches color, colour
Limitations:
- Cannot use at beginning of search term
- May retrieve unexpected variations
Proximity Searching
Search for terms within a specified distance from each other. Only available in Title, Title/Abstract, and Affiliation fields.
Syntax: "search terms"[field:~N]
- N = maximum number of words between terms
Examples:
"vitamin C"[Title:~3] → vitamin within 3 words of C in title
"breast cancer screening"[TIAB:~5] → terms within 5 words in title/abstract
Search Field Tags
Field tags limit searches to specific parts of PubMed records. Format: term[tag]
Author Searching
| Tag | Field | Example |
|---|---|---|
| [au] | Author | smith j[au] |
| [1au] | First Author | jones m[1au] |
| [lastau] | Last Author | wilson k[lastau] |
| [fau] | Full Author Name | smith john a[fau] |
Author Search Notes:
- Full author names searchable from 2002 forward
- Format: last name + initials (e.g.,
smith ja[au]) - Can search without field tag, but [au] ensures accuracy
Corporate Authors: Search organizations as authors:
world health organization[au]
Title and Abstract
| Tag | Field | Example |
|---|---|---|
| [ti] | Title | diabetes[ti] |
| [ab] | Abstract | treatment[ab] |
| [tiab] | Title/Abstract | cancer screening[tiab] |
| [tw] | Text Word | cardiovascular[tw] |
Notes:
- [tw] searches title, abstract, and other text fields
- [tiab] is most commonly used for comprehensive searching
Journal Information
| Tag | Field | Example |
|---|---|---|
| [ta] | Journal Title Abbreviation | Science[ta] |
| [jour] | Journal | New England Journal of Medicine[jour] |
| [issn] | ISSN | 0028-4793[issn] |
Date Fields
| Tag | Field | Format | Example |
|---|---|---|---|
| [dp] | Publication Date | YYYY/MM/DD | 2023[dp] |
| [edat] | Entrez Date | YYYY/MM/DD | 2023/01/15[edat] |
| [crdt] | Create Date | YYYY/MM/DD | 2023[crdt] |
| [mhda] | MeSH Date | YYYY/MM/DD | 2023[mhda] |
Date Ranges: Use colon to specify ranges:
2020:2023[dp] → publications from 2020 to 2023
2023/01/01:2023/06/30[dp] → first half of 2023
Relative Dates: PubMed filters provide common ranges:
- Last 1 year
- Last 5 years
- Last 10 years
- Custom date range
MeSH and Subject Headings
| Tag | Field | Example |
|---|---|---|
| [mh] | MeSH Terms | diabetes mellitus[mh] |
| [majr] | MeSH Major Topic | hypertension[majr] |
| [mesh] | MeSH Terms | cancer[mesh] |
| [sh] | MeSH Subheading | therapy[sh] |
MeSH Searching:
- Medical Subject Headings provide controlled vocabulary
- [mh] includes narrower terms automatically
- [majr] limits to articles where topic is main focus
- Combine with subheadings:
diabetes mellitus/therapy[mh]
Common MeSH Subheadings:
- /diagnosis
- /drug therapy
- /epidemiology
- /etiology
- /prevention & control
- /therapy
Publication Types
| Tag | Field | Example |
|---|---|---|
| [pt] | Publication Type | clinical trial[pt] |
| [ptyp] | Publication Type | review[ptyp] |
Common Publication Types:
- Clinical Trial
- Meta-Analysis
- Randomized Controlled Trial
- Review
- Systematic Review
- Case Reports
- Letter
- Editorial
- Guideline
Example:
cancer AND systematic review[pt]
Other Useful Fields
| Tag | Field | Example |
|---|---|---|
| [la] | Language | english[la] |
| [affil] | Affiliation | harvard[affil] |
| [pmid] | PubMed ID | 12345678[pmid] |
| [pmc] | PMC ID | PMC123456[pmc] |
| [doi] | DOI | 10.1234/example[doi] |
| [gr] | Grant Number | R01CA123456[gr] |
| [isbn] | ISBN | 9780123456789[isbn] |
| [pg] | Pagination | 123-145[pg] |
| [vi] | Volume | 45[vi] |
| [ip] | Issue | 3[ip] |
Supplemental Concepts
| Tag | Field | Example |
|---|---|---|
| [nm] | Substance Name | aspirin[nm] |
| [ps] | Personal Name | darwin charles[ps] |
Automatic Term Mapping (ATM)
When searching without field tags, PubMed automatically:
- Searches MeSH translation table for matching MeSH terms
- Searches journal translation table for journal names
- Searches author index for author names
- Searches full text for remaining terms
Bypass ATM:
- Use double quotes:
"breast cancer" - Use field tags:
breast cancer[tiab]
View Translation: Use Advanced Search to see how PubMed translated your query in the Search Details box.
Filters and Limits
Article Types
- Clinical Trial
- Meta-Analysis
- Randomized Controlled Trial
- Review
- Systematic Review
Text Availability
- Free full text
- Full text
- Abstract
Publication Date
- Last 1 year
- Last 5 years
- Last 10 years
- Custom date range
Species
- Humans
- Animals (specific species available)
Sex
- Female
- Male
Age Groups
- Child (0-18 years)
- Infant (birth-23 months)
- Child, Preschool (2-5 years)
- Child (6-12 years)
- Adolescent (13-18 years)
- Adult (19+ years)
- Aged (65+ years)
- 80 and over
Languages
- English
- Spanish
- French
- German
- Chinese
- And many others
Other Filters
- Journal categories
- Subject area
- Article attributes (e.g., has abstract, free PMC article)
Advanced Search Strategies
Clinical Queries
PubMed provides specialized filters for clinical research:
Study Categories:
- Therapy (narrow/broad)
- Diagnosis (narrow/broad)
- Etiology (narrow/broad)
- Prognosis (narrow/broad)
- Clinical prediction guides
Medical Genetics:
- Diagnosis
- Differential diagnosis
- Clinical description
- Management
- Genetic counseling
Hedges and Filters
Pre-built search strategies for specific purposes:
- Systematic review filters
- Quality filters for study types
- Geographic filters
Combining Searches
Use Advanced Search to combine previous queries:
#1 AND #2
#3 OR #4
#5 NOT #6
Search History
- Saves up to 100 searches
- Expires after 8 hours of inactivity
- Access via Advanced Search page
- Combine using # references
Best Practices
1. Start Broad, Then Narrow
Begin with general terms and add specificity:
diabetes → too broad
diabetes mellitus type 2 → better
diabetes mellitus type 2[mh] AND treatment[tiab] → more specific
2. Use Synonyms with OR
Include alternative terms:
heart attack OR myocardial infarction OR MI
3. Combine Concepts with AND
Link different aspects of your research question:
(heart attack OR myocardial infarction) AND (aspirin OR acetylsalicylic acid) AND prevention
4. Leverage MeSH Terms
Use MeSH for consistent indexing:
diabetes mellitus[mh] AND hypertension[mh]
5. Use Filters Strategically
Apply filters to refine results:
- Publication date for recent research
- Article type for specific study designs
- Free full text for accessible articles
6. Review Search Details
Check how PubMed interpreted your search in Advanced Search to ensure accuracy.
7. Save Effective Searches
Create My NCBI account to:
- Save searches
- Set up email alerts
- Create collections
Common Search Patterns
Systematic Review Search
(breast cancer[tiab] OR breast neoplasm[mh]) AND (screening[tiab] OR early detection[tiab]) AND systematic review[pt]
Clinical Trial Search
diabetes mellitus type 2[mh] AND metformin[nm] AND randomized controlled trial[pt] AND 2020:2024[dp]
Recent Research by Author
smith ja[au] AND cancer[tiab] AND 2023:2024[dp] AND english[la]
Drug Treatment Studies
hypertension[mh] AND (amlodipine[nm] OR losartan[nm]) AND drug therapy[sh] AND humans[mh]
Geographic-Specific Research
malaria[tiab] AND (africa[affil] OR african[tiab]) AND 2020:2024[dp]
Special Characters
| Character | Purpose | Example |
|---|---|---|
| * | Wildcard | colo*r |
| " " | Phrase search | "breast cancer" |
| ( ) | Group terms | (A OR B) AND C |
| : | Range | 2020:2023[dp] |
| - | Hyphenated terms | COVID-19 |
| / | MeSH subheading | diabetes/therapy[mh] |
Troubleshooting
Too Many Results
- Add more specific terms
- Use field tags to limit search scope
- Apply date restrictions
- Use filters for article type
- Add additional concepts with AND
Too Few Results
- Remove restrictive terms
- Use OR to add synonyms
- Check spelling and terminology
- Remove field tags for broader search
- Expand date range
- Remove filters
No Results
- Check spelling using ESpell
- Try alternative terminology
- Remove field tags
- Verify correct database (PubMed vs. PMC)
- Broaden search terms
Unexpected Results
- Review Search Details to see query translation
- Use field tags to prevent automatic term mapping
- Check for common synonyms that may be included
- Refine with additional limiting terms