DATABASES: MEDICAL HEALTH BIOSCIENCES BIOLOGY PSYCHOLOGY:
Google Scholar Retrieves Twice as Many Relevant Citations as PubMed
and Provides Greater Full-Text Access
for Quick, Clinical Nephrology Searches
Google Scholar Retrieves Twice as Many Relevant Citations as PubMed and
Provides Greater Full-Text Access for Quick, Clinical Nephrology Searches
A Review of:
Shariff, S. Z., Bejaimal, S. A. D., Sontrop, J. M., Iansavichus, A. V.,
Haynes, R. B., Weir, M. A., & Garg, A. X. (2013).
Retrieving clinical evidence:
A comparison of PubMed and Google Scholar for quick clinical
Journal of Medical Internet Research,
Diana K. Wakimoto
Online Literacy Librarian
California State University, East Bay
Hayward, California, United States of America
Email: [log in to unmask]
Received: 15 Oct. 2013 Accepted: 6 Feb. 2014
Evidence Based Library Information and Practice
Vol 9, No 1 (2014)
A shorter URL for the above link:
Objective To compare recall and precision of results retrieved by
searches in PubMed and Google Scholar for clinical nephrology literature.
Design Survey questionnaire, comparative.
Subjects Practicing nephrologists with average age of 48 years and who
have practiced nephrology for an average of 15 years.
Methods The researchers identified 100 systematic reviews in renal
therapy published between 2001 and 2009. The primary studies cited in the
systematic reviews served as the reference standard for relevant articles;
1,574 unique citations were identified and used to measure recall and
Results Google Scholars recall for the first 40 records was 21.9% and
PubMed was 10.9%. Each database contained 78% of the relevant
literature/reference standard set from the systematic reviews. However,
15% of the articles were in neither database. Precision results were
similar (7.6% for Google Scholar and 5.6% for PubMed). Google Scholar had
more full-text available at 15% of articles versus 5% for PubMed. Google
Scholar and PubMed had similar numbers of relevant articles when all
retrieved records were analyzed, but Google Scholar still provided more
access to free full-text articles.
Conclusion Google Scholar provides better recall and provides more access
to full-text than PubMed; however, search strings provided by
nephrologists used in both databases failed to retrieve 80% of relevant
articles. Therefore improving nephrologists ability to effectively search
could enhance their ability to implement research in practice helping
This research article is significant in its rigorous comparison of Google
Scholar and PubMed and provides valuable insight for medical librarians,
and possibly librarians who work in other fields as well. As more people
use Google Scholar for quickly finding research to use in clinical
therapy, it is important that librarians understand the strengths and
weaknesses of the database and its place in literature searching. As the
researchers note that most nephrologists view fewer than 40 search
results, it would be interesting to replicate the study given PubMeds
recently introduced relevancy ranking, a feature that may have given
Google Scholar the edge in retrieving more relevant results in the first
Retrieving Clinical Evidence: A Comparison of PubMed and Google Scholar
for Quick Clinical Searches
Salimah Z Shariff, Shayna AD Bejaimal, Jessica M Sontrop, Arthur V
Iansavichus, R Brian Haynes, Matthew A Weir, Amit X Garg
J Med Internet Res 2013 (Aug 15); 15(8):e164
Salimah Z Shariff1,2, BMath, PhD; Shayna AD Bejaimal1, BMedSc; Jessica M
Sontrop1,2, PhD; Arthur V Iansavichus1, MLIS; R Brian Haynes3,4, MD, PhD;
Matthew A Weir1, MD; Amit X Garg1,2,3, MD, PhD
1Kidney Clinical Research Unit, Division of Nephrology, Western
University, London, ON, Canada
2Department of Epidemiology and Biostatistics, Western University, London,
3McMaster University, Department of Clinical Epidemiology and
Biostatistics, Hamilton, ON, Canada
4Department of Medicine, McMaster University, Hamilton, ON, Canada
Salimah Z Shariff, BMath, PhD
Kidney Clinical Research Unit
Division of Nephrology
800 Commissioners Rd E. Rm ELL-108
London, ON, N6A 4G5
Phone: 1 519 685 8500 ext 56555
Fax: 1 519 685 8072
Email: salimah.shariff [at] lhsc.on.ca
Background: Physicians frequently search PubMed for information to guide
patient care. More recently, Google Scholar has gained popularity as
another freely accessible bibliographic database.
Objective: To compare the performance of searches in PubMed and Google
Methods: We surveyed nephrologists (kidney specialists) and provided each
with a unique clinical question derived from 100 renal therapy systematic
reviews. Each physician provided the search terms they would type into a
bibliographic database to locate evidence to answer the clinical question.
We executed each of these searches in PubMed and Google Scholar and
compared results for the first 40 records retrieved (equivalent to 2
default search pages in PubMed). We evaluated the recall (proportion of
relevant articles found) and precision (ratio of relevant to nonrelevant
articles) of the searches performed in PubMed and Google Scholar. Primary
studies included in the systematic reviews served as the reference
standard for relevant articles. We further documented whether relevant
articles were available as free full-texts.
Results: Compared with PubMed, the average search in Google Scholar
retrieved twice as many relevant articles (PubMed: 11%; Google Scholar:
22%; P<.001). Precision was similar in both databases (PubMed: 6%; Google
Scholar: 8%; P=.07). Google Scholar provided significantly greater access
to free full-text publications (PubMed: 5%; Google Scholar: 14%; P<.001).
Conclusions: For quick clinical searches, Google Scholar returns twice as
many relevant articles as PubMed and provides greater access to free
Nourbakhsh, E., Nugent, R., Wang, H., Cevik, C., & Nugent, K.
Medical literature searches: A comparison of PubMed and Google Scholar.
Health Information and Libraries Journal,
This article is full text in the fee based Academic Search Premier
database from EBSCOHost and in the Wiley-Blackwell Full Collection
journal aggregation service.
More on Google Scholar and PubMed
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The complete articles may be read at the URLs provided for each.
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