Step Two – Choose the right literature resources
Once you have a better idea of what you need from the literature review, the next step is to determine which databases have the best results for the field of interest. In general, the four most important databases in the medical scientific field are MEDLINE, EMBASE, SCISEARCH and BIOSIS, but this is by no means guaranteed for any particular search requirement. For example, for health economics topics it may be better to use the HEED bibliographic database; for safety data TOXFILE might be useful; in another setting a good database to use might be the Cochrane literature reviews. Rx uses ProQuest – a search engine that accesses 64 relevant databases and that recently superseded Datastar. The search engine used will have some effect on the results, but in general it is best to use one that allows the removal of duplicates – otherwise costs increase considerably. However, if other databases or sources (e.g. abstract books, grey literature) are deemed to be important but are not available by the main search engine, these can be added to the results and de-duped manually.
Normally, for a comprehensive search strategy, Rx would use the top 4 databases that retrieve the most citations; particularly if the number of duplicates is low. PubMed is a logical start because it doesn’t cost anything, but researchers should be aware that PubMed and MEDLINE are not exactly the same entities, and the search engine change from PubMed to MEDLINE can also make a slight difference to the results. Depending on the therapeutic area in question, PubMed will usually pick up between 60 and 80% of the available published full papers; hence the need to use more than one literature source if the results must be definitive. We always include some form of benchmarking for databases and search engines to get a feel for the margin of error.