Of recent interest to medical librarians is an article that was published in BMJ regarding search results in PubMed and how evidence from randomized clinical trials is retrieved. Here is some updated information from the National Library of Medicine, Bibliographic Services Division:
Re: Wieland LS, Robinson KA, Dickersin K. Understanding why evidence from randomised clinical trials may not be retrieved from Medline: comparison of
indexed and non-indexed records. BMJ. 2012 Jan 3;344:d7501. doi: 10.1136/bmj.d7501. PubMed PMID: 22214757.
Readers of this article should recognize that the authors assumed no changes took place in the NLM indexing of Randomized Controlled Trial
[publication type]. In fact, NLM has made changes since 2005 that we think affect the conclusions and projections made in the article. These changes
1. Since 2005, we conduct a monthly PubMed quality assurance search to review completed citations that are candidates for Randomized Controlled
Trial [publication type] but lack that tag. Appropriate edits are made to add that Publication Type when it has been missed (per the NLM definition
of Randomized Controlled Trial [publication type] which is “for original report of the conduct or results of a specific randomized controlled trial”).
2. Since 2007, we have broadened our indexing practice for Randomized Controlled Trial [publication type] to include follow-up, post hoc analysis
and the like of specific trials.
Together these two changes ensure that NLM indexers are appropriately tagging MEDLINE citations with Randomized Controlled Trial [publication type]
for the researcher and clinician audience.
Deputy Chief, Bibliographic Services Division
National Library of Medicine