Google Scholar vs. MEDLINE for Health Sciences Literature Searching

Google Scholar vs. MEDLINE for Health Sciences Literature Searching Patricia M. Weiss, MLIS Health Sciences Library System University of Pittsburgh March 19, 2008

About MEDLINE

Largest database of indexed journal citations for health sciences literature

Indexed records = Organized records that include standard descriptors of topics

>16 million citations from 5000 journals back to 1949

Produced by National Library of Medicine (NLM), one of the National Institutes of Health

About MEDLINE

Available with different interfaces developed by different organizations

Interface = screen you see + search engine in background

HSLS supported versions

PubMed (from NLM)

Ovid MEDLINE (from Ovid Corporation)

Other versions (ClusterMed, Web of Science, EBSCOhost, etc.) look different but have the same raw data.

PubMed

Ovid MEDLINE

MEDLINE Database

Fields in a MEDLINE Record

NLM’s PubMed Ovid MEDLINE

Journals Included in MEDLINE

List of journals is easy to find and refer to.

Information about coverage is clearly stated.

MeSH ( Me dical S ubject H eadings)

MeSH = Organized hierarchical “tree” system of standardized terms used to index all articles

Articles on the same topic are indexed with the same term, even if authors use different terms for same concept.

As opposed to: Searching for a particular string of characters (“textword” or “keyword” searching)

Fields in a MEDLINE Record

Different Terms, Same MeSH

Title #1

Treatment of

gastric cancer .

Title #2 Technical considerations in laparoscopic resection of gastric neoplasms . MeSH headings for both titles : Stomach Neoplasms

Same Term, Different MeSH

Title #1

The diagnosis of plaque - induced periodontal diseases.

MeSH heading:

Dental Plaque

Title #2 Mechanism of senile plaque formation in Alzheimer disease. MeSH heading: Senile Plaques

MEDLINE Strengths

You are searching the bulk of health sciences literature.

Easy to determine if a journal is included and how far back it goes

All articles from important journals are included.

Concept as well as textword searching

MEDLINE Limitations

MeSH has a learning curve, can be difficult to use well.

MeSH indexers aren’t infallible; indexing can be inconsistent.

MEDLINE record includes information about article but not full text of the article.

Search results are typically ranked by date, not relevance.

It takes time for articles to be processed and MeSH terms to be assigned.

MEDLINE Limitations

New journals generally not included until they have proven themselves over several years

Includes primarily journals related to the health sciences and a few major journals from related disciplines

Does not include health-related articles from journals in other disciplines

About Google Scholar

Google “harvests” information from full-text articles with publisher permission, then makes them fully searchable.

Not all publishers are included.

Also includes books, free and “open source” resources, digital libraries, and other scholarly sources on the Web

2 different types of entries

Main entries for publication itself

Mini-entries for cited references that GS cannot find online. [citation]

From GS Help Anatomy of a Google Scholar Record

Full-text searching

Lets you search for specific details in the article itself (place, substance, personal names)

Relevancy ranking

Covers literature from many disciplines and from non-journal sources

Scopus and ISI Web of Science do this, too.

GS does it, MEDLINE doesn’t:

GS Limitations

No consistent format for journal titles –

Need to search on full title and maybe several possible abbreviations to find everything

Publication Date is not always captured and not always visible in the full text.

A search for documents published in 2005, would not retrieve 2005 items with no date listed.

Scope of Google Scholar?????

MEDLINE: >16 million articles back to 1940s

GS: #??? articles back to 19##???

GS Limitations: The Denominator Problem

Is database coverage well-documented?

If not, how do you know what you’re missing?

Is the database concept indexed with standardized terms?

If not, can you think of all the different text strings that might elicit retrieval?

(And if not, how do you know what you’re missing?)

2008 2007

GS Limitations: Keyword Searching

No standardized terms for concepts You’re on your own with trying to think up all the different terms an author might use to evoke a particular context.

GS general vocabulary resource is Answers.com

MeSH developed by NLM

Stedman’s Medical Dictionary originally a main source

Google Scholar Summary

Search results ranked by relevance

Links to citing references + secondary records for cited references not otherwise included

Export to EndNote, RefWorks is possible.

Number of records unknown

Journals plus books and other information types depending on institutional configuration

Coverage (which journals?) unknown

Multidisciplinary; subject area limits available

Other Multidisciplinary Indexes: Scopus and Web of Science

Scopus (from Elsevier; 29 million abstracts, >15K journals, back to 1966; sciences + social sciences)

WoS’ Science Citation Index Expanded (from Thomson; >6,650 major journals as far back as 1900 in 150 scientific disciplines)

May include MEDLINE records, but no standardized terms of their own

Citing and cited reference lists

Easy export to EndNote, RefWorks

Product Feature Comparison Google Scholar MEDLINE (via PubMed) Web of Science Scopus Concept searching?    some Sources list (which journals, etc.)?     Cited reference list?     Citing reference list?     Export to EndNote, RefWorks?  manual import   Score 40% 50% 60% 90%

Bottom Line: Both Tools are Useful