Pubmed Database

Construct sophisticated PubMed queries using Boolean operators, field tags, and specialized syntax.

Basic Search Strategies:

• Combine concepts with Boolean operators (AND, OR, NOT)
• Use field tags to limit searches to specific record parts
• Employ phrase searching with double quotes for exact matches
• Apply wildcards for term variations
• Use proximity searching for terms within specified distances

Example Queries:

# Recent systematic reviews on diabetes treatment
diabetes mellitus[mh] AND treatment[tiab] AND systematic review[pt] AND 2023:2024[dp]

# Clinical trials comparing two drugs
(metformin[nm] OR insulin[nm]) AND diabetes mellitus, type 2[mh] AND randomized controlled trial[pt]

# Author-specific research
smith ja[au] AND cancer[tiab] AND 2023[dp] AND english[la]

When to consult search_syntax.md:

• Need comprehensive list of available field tags
• Require detailed explanation of search operators
• Constructing complex proximity searches
• Understanding automatic term mapping behavior
• Need specific syntax for date ranges, wildcards, or special characters

Grep pattern for field tags: \[au\]|\[ti\]|\[ab\]|\[mh\]|\[pt\]|\[dp\]

2. MeSH Terms and Controlled Vocabulary

Use Medical Subject Headings (MeSH) for precise, consistent searching across the biomedical literature.

MeSH Searching:

• [mh] tag searches MeSH terms with automatic inclusion of narrower terms
• [majr] tag limits to articles where the topic is the main focus
• Combine MeSH terms with subheadings for specificity (e.g., diabetes mellitus/therapy[mh])

Common MeSH Subheadings:

• /diagnosis - Diagnostic methods
• /drug therapy - Pharmaceutical treatment
• /epidemiology - Disease patterns and prevalence
• /etiology - Disease causes
• /prevention & control - Preventive measures
• /therapy - Treatment approaches

Example:

# Diabetes therapy with specific focus
diabetes mellitus, type 2[mh]/drug therapy AND cardiovascular diseases[mh]/prevention & control

3. Article Type and Publication Filtering

Filter results by publication type, date, text availability, and other attributes.

Publication Types (use [pt] field tag):

• Clinical Trial
• Meta-Analysis
• Randomized Controlled Trial
• Review
• Systematic Review
• Case Reports
• Guideline

Date Filtering:

• Single year: 2024[dp]
• Date range: 2020:2024[dp]
• Specific date: 2024/03/15[dp]

Text Availability:

• Free full text: Add AND free full text[sb] to query
• Has abstract: Add AND hasabstract[text] to query

Example:

# Recent free full-text RCTs on hypertension
hypertension[mh] AND randomized controlled trial[pt] AND 2023:2024[dp] AND free full text[sb]

4. Programmatic Access via E-utilities API

Access PubMed data programmatically using the NCBI E-utilities REST API for automation and bulk operations.

Core API Endpoints:

1. ESearch - Search database and retrieve PMIDs
2. EFetch - Download full records in various formats
3. ESummary - Get document summaries
4. EPost - Upload UIDs for batch processing
5. ELink - Find related articles and linked data

Basic Workflow:

import requests

# Step 1: Search for articles
base_url = "https://eutils.ncbi.nlm.nih.gov/entrez/eutils/"
search_url = f"{base_url}esearch.fcgi"
params = {
    "db": "pubmed",
    "term": "diabetes[tiab] AND 2024[dp]",
    "retmax": 100,
    "retmode": "json",
    "api_key": "YOUR_API_KEY"  # Optional but recommended
}
response = requests.get(search_url, params=params)
pmids = response.json()["esearchresult"]["idlist"]

# Step 2: Fetch article details
fetch_url = f"{base_url}efetch.fcgi"
params = {
    "db": "pubmed",
    "id": ",".join(pmids),
    "rettype": "abstract",
    "retmode": "text",
    "api_key": "YOUR_API_KEY"
}
response = requests.get(fetch_url, params=params)
abstracts = response.text

Rate Limits:

• Without API key: 3 requests/second
• With API key: 10 requests/second
• Always include User-Agent header

Best Practices:

• Use history server (usehistory=y) for large result sets
• Implement batch operations via EPost for multiple UIDs
• Cache results locally to minimize redundant calls
• Respect rate limits to avoid service disruption

When to consult api_reference.md:

• Need detailed endpoint documentation
• Require parameter specifications for each E-utility
• Constructing batch operations or history server workflows
• Understanding response formats (XML, JSON, text)
• Troubleshooting API errors or rate limit issues

Grep pattern for API endpoints: esearch|efetch|esummary|epost|elink|einfo

5. Citation Matching and Article Retrieval

Find articles using partial citation information or specific identifiers.

By Identifier:

# By PMID
12345678[pmid]

# By DOI
10.1056/NEJMoa123456[doi]

# By PMC ID
PMC123456[pmc]

Citation Matching (via ECitMatch API): Use journal name, year, volume, page, and author to find PMIDs:

Format: journal|year|volume|page|author|key|
Example: Science|2008|320|5880|1185|key1|

By Author and Metadata:

# First author with year and topic
smith ja[1au] AND 2023[dp] AND cancer[tiab]

# Journal, volume, and page
nature[ta] AND 2024[dp] AND 456[vi] AND 123-130[pg]

6. Systematic Literature Reviews

Conduct comprehensive literature searches for systematic reviews and meta-analyses.

PICO Framework (Population, Intervention, Comparison, Outcome): Structure clinical research questions systematically:

# Example: Diabetes treatment effectiveness
# P: diabetes mellitus, type 2[mh]
# I: metformin[nm]
# C: lifestyle modification[tiab]
# O: glycemic control[tiab]

diabetes mellitus, type 2[mh] AND
(metformin[nm] OR lifestyle modification[tiab]) AND
glycemic control[tiab] AND
randomized controlled trial[pt]

Comprehensive Search Strategy:

# Include multiple synonyms and MeSH terms
(disease name[tiab] OR disease name[mh] OR synonym[tiab]) AND
(treatment[tiab] OR therapy[tiab] OR intervention[tiab]) AND
(systematic review[pt] OR meta-analysis[pt] OR randomized controlled trial[pt]) AND