Foreground information answers specific questions a clinician has regarding a specific patient. Foreground resources can be divided into primary sources such as original research articles published in journals; and secondary sources such as systematic reviews of the topic, and synopses and reviews of individual studies.
A Primary Source is firsthand testimony or direct evidence concerning a topic under investigation. Primary resources are generally articles that appear in peer-reviewed journals and are found primarily by searching MedLine.
Secondary sources are summaries and analyses of the evidence derived from and based on primary sources. A secondary source is a work that appraises, interprets or analyzes. It is generally at least one step removed from the evidence. Secondary resources available on the Library's EBM Resource Page include Clinical Evidence, ACP Journal Club, and Cochrane Library.
If you have a choice, you may make better use of your time by searching first in secondary resources. Provided you trust the organization producing the resource (e.g. The American College of Physicians), you can rely on their judgment regarding the critical analysis of the studies. Another benefit of some secondary resources (e.g. Clinical Evidence) is that you will be able to rely on the results of several studies instead of just the one reported in a primary report.