Tsay MY and Yang YH " Bibliometric analysis of the literature of randomized controlled trials" Journal of the Medical Library Association Vol:93, #4, p.450-458, October 2005.
eugene.garfield at THOMSON.COM
Tue Oct 25 15:41:57 EDT 2005
E-mail: Ming-Yueh Tsay : mytsay at nccu.edu.tw
Yen-hsu Yang : luga at tmu.edu.tw
Title : Bibliometric analysis of the literature of randomized controlled
Author : Ming-yueh Tsay, PhD,Professor and Yen-hsu Yang, MA, Librarian
Source : Journal of the Medical Library Association, Vol:93, Number 4,
October 2005, p.450-458
Table 5 in the following paper lists the 42 core journals identified in the
study and gives the number of articles with randomized controlled trials
and Impact Factor and Subject category.
Objective: Evidence-based medicine (EBM) is a significant issue and the
randomized controlled trial (RCT) literature plays a fundamental role in
developing EBM. This study investigates the features of RCT literature
based on bibliometric methods. Growth of the literature, publication types,
languages, publication countries, and research subjects are addressed. The
distribution of journal articles was also examined utilizing Bradford's law
and Bradford-Zipf's law.
Method: The MEDLINE database was searched for articles indexed under the
publication type Randomized Control Trial, and articles retrieved were
counted and analyzed using Microsoft Access, Microsoft Excel, and PERL.
Results: From 1990 to 2001, a total of 114,850 citations dealing with RCTs
were retrieved. The literature growth rate, from 1965 to 2001, is steadily
rising and follows an exponential model. Journal articles are the
predominant form of publication, and the multicenter study is extensively
used. English is the most commonly used language.
Conclusions: Generally, RCTs are found in publications concentrating on
cardiovascular disease, cancer, asthma, postoperative conditon, health, and
anesthetics. Zone analysis and graphical formulation from Bradford's law of
scattering shows variations from the standard Bradford model. Forty-two
core journals were identified using Bradford's law.
SUMMARY AND CONCLUSIONS
This study investigated the growth of RCT literature, based on the MEDLINE
database, and explored the various features of the literature using well-
established bibliometric methods. The results are summarized as follows:
1. The RCT literature from 1965 to 2001 grew exponentially, indicating
that the growth of the literature using RCTs maintains a constant rate for
the period of the study. The best fit of data reveals that the yearly
growth rate is about 11.2%.
2. The single most common form of publication covered in MEDLINE is the
journal article, which contributes about 98% of the total RCT literature
3. Analyzing the publication type demonstrated that, for articles where
that level of detail is indicated, the multicenter study is the most widely
employed (73.63%), followed by phase II clinical trials (5.38%) and phase
III clinical trials (5.34%).
4. The United States of America is the predominant publishing country in
the RCT literature (about 39.9% of the journals and 50.6% of the articles).
English is the most common language. English articles constitute 92.9% of
5. The subject areas are diverse and widely dispersed. The areas that
employed RCT methods the most include drug therapy for hypertension,
therapeutic use of combined antineoplastic agents, and drug therapy in
6. Forty-two core journals containing 25% of the RCT journal literature
can be identified from Bradford zone analysis and the Bradford-Zipf plot.
However, the total journal literature is widely spread among many different
journals. About half of literature is concentrated in 147 journals, while
the remaining half is scattered in 2,701 journals. Moreover, 481 of the
journals in the study published only 1 paper.
7. The analysis of the core journals indicates that (1) the more
frequently a journal is published, the more productive it is likely to be;
(2) most of the core journals deal with anesthesia, pharmacology and
pharmacy, cardiac and cardiovascular systems, and general and internal
medicine; and (3) journals with impact factors greater than ten are related
to general and internal medicine.
The information on literature growth, key concepts, and journal features
provided by the present study should be of significant interest for
understanding the development of RCTs and the design of modern information
retrieval systems. For example, the study of journal characteristics
facilitates establishing a baseline for librarians in making decisions
about journal subscriptions and cancellations in the RCT area. The nucleus
journals (with a high productivity) identified by Bradford's law usually
contain more relevant articles in the area, and, thus, subscriptions to
such journals would be worthwhile. Inclusion of these journals in indexing
and abstracting services would be justified scientifically. Furthermore,
physicians may focus on these core journals as they are usually very busy,
and these core journals would cover 25% of the literature on RCTs from 1990
to 2001. Subscribing to journals with low productivity would be
unnecessary, and these journals could be discarded. Additionally, core
journals can help direct readers to those journals that publish highly
relevant articles. From the key concepts and publication types, the
intellectual structure and development in the area of RCT research can be
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