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Letter to the Editor

In a short report published in Laboratory Animals in October 2011, we presented a search filter for the maximum retrieval of animal studies from the bibliographic database Embase. This search filter greatly facilitates the search for animal experiments in this large biomedical database, just as a similar search filter does for PubMed. Collecting and analysing all relevant animal research data are important before starting a new animal experiment and are indispensable when writing systematic reviews of animal research. In this letter to the editor, an updated version of the Embase search filter is presented. The former version of the filter does not work adequately anymore, because of alterations in ‘Emtree’, the Elsevier life science thesaurus. A thesaurus is a hierarchically structured, controlled vocabulary for efficiently searching the database in question. The functioning of the search filter critically depends on the way in which the thesaurus terms are related to one another. As of January 2013, the Emtree term human/ is included in the Emtree term Chordata/, which in itself is part of the Emtree term animal/ (http://www.elsevier. com/online-tools/embase/emtree). Previously, the Emtree terms human/ and animal/ were in separate branches of the tree. As a consequence of the altered relation between human/ and animal/, the former version of the filter started to include all studies that used humans (and no other animals) as subjects, whereas the filter was intended to exclude exactly this type of studies. We have adapted the ‘mode’ in which the Emtree terms animal/ and Chordata/ are present in the search filter, so that the filter no longer automatically includes the purely human studies. The total number of records the updated search filter retrieves on its own (5,884,276) and in combination with a search strategy specific for the topic pancreatitis and probiotics (83) are similar to those in the original version of the filter (search date 3 May 2013). The new version of the search filter (version 2; 31 January 2013) can be found in Supplement 1 (see http://lan.sagepub.com/content/48/ 1/88/suppl/DC1). The Embase thesaurus is updated three times a year. It is likely that some of these updates will affect the functioning of our search filter. For that reason, we will check each time the thesaurus is updated to see whether our search filter still works properly. If not, we will make the necessary changes to the filter and replace the version now presented in Supplement 1 (see above link). In this way, the most updated version of the search filter will always be available online and it will remain easy to identify all the animal studies on a particular topic in Embase.