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J Med Libr Assoc. 2005 Oct;93(4):450-8.

Bibliometric analysis of the literature of randomized controlled trials.

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Graduate Institute of Library, Information and Archival Studies National Chengchi University Taipei, Taiwan, Republic of China.



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.


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.


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.


Generally, RCTs are found in publications concentrating on cardiovascular disease, cancer, asthma, postoperative condition, 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.

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