Searching the MEDLINE literature database through PubMed: a short guide.

The Medline database from the National Library of Medicine (NLM) contains more than 12 million bibliographic citations from over 4,600 international biomedical journals. One of the interfaces for searching Medline is PubMed, provided by the NLM for free access via the Internet (www.pubmed.gov). Also searchable with the PubMed interface are non-Medline citations, i.e. articles supplied by publishers to the NLM. Direct access to an electronic full text version is also possible if the article is available from a publisher or institution participating in Linkout (www.ncbi.nlm.nih.gov/entrez/linkout/). Some publishers provide free access to their journals. Other journals require an online license and are fee based. The following example demonstrates some of the most important search functions in PubMed. We will start out with a fast and simple approach without the use of specific searching techniques and then continue with a more sophisticated search that requires the knowledge of Medline search functions. This example will show how the application of Medline search tools and how the use of the controlled vocabulary of 'Medical Subject Headings' (MeSH) will influence the results in comparison with the fast and simple approach. Let's try to find the best evidence to answer the following question: Is a 30-year-old man with typical acid reflux symptoms for many years (gastroesophageal reflux disease, GERD) more likely to develop esophageal cancer than people without reflux symptoms? This question can be split into several components: -a patient with reflux symptoms (GERD), -esophageal cancer: etiology, risk, -study design for etiology studies: cohort studies, case-control studies.