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Acta Medica Colombiana

Print version ISSN 0120-2448


MARTINEZ-FRANCO, MARIANA; NIRTA-PEREZ, ANTONIO ROBERTO  and  DONADO-GOMEZ, JORGE HERNANDO. Types of randomized clinical trials published in PubMed over 40 years. Acta Med Colomb [online]. 2021, vol.46, n.2, pp.26-33.  Epub Nov 21, 2021. ISSN 0120-2448.


there are several variations of randomized clinical trials. Trials can be classi fied by design as parallel, cross-over, factorial, assignment by group, n-of-1, paired, withdrawal, adaptive and pragmatic; and by purpose as superiority, non-inferiority and equivalence. Given this heterogeneity, the Consolidated Standards of Reporting Trials (CONSORT) were introduced in 1996 to provide a guideline for reporting randomized clinical trials.


to describe the publication tendency of the various types of randomized clinical trials over 40 years, with reference to the publication of CONSORT and its extensions.


the PubMed tool was used to search for randomized clinical trials published between 1979 and 2018, classifying them according to the varieties described.


a total of 472,114 published articles were found; 90.2% did not report the type of design and 98.2% did not report the purpose. Among the articles that reported the variety of randomized clinical trial, the predominant design was cross-over (5.9%), followed by parallel groups (2.34%); while the most common purpose was superiority (0.84%). After the launch of CONSORT, there was an increased proportion of articles published with the following designs: parallel groups; difference in proportions 1.89 95% CI (1.1-2.7); paired 1.07 95% CI (0.2-1.9); and pragmatic 4.73 95% CI (4.4-5.1); and for the purpose of non-inferiority 5.97 95% CI (5.6-6.3).


most articles on randomized clinical trials do not mention their type in the title and abstract. The proportion of articles that did, increased slightly after CONSORT was published. (Acta Med Colomb 2021; 46. DOI:

Keywords : clinical trial; epidemiological study design; publications; epidemiological study characteristics; assessment of therapeutic intervention results.

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