(2004; 45 pages)
Secondary information sources
Secondary sources either review the primary literature or direct a researcher to it, as described below:
1. Reviews are presented as systematic reviews, secondary journal publications (critical appraisal comments added to the abstract of a primary article), clinical practice guidelines, health technology assessments or drug information bulletins. They all review the original evidence and may draw additional conclusions about it. They can be fairly up-to-date, and if the review process has followed a rigorous method such as that used by the Cochrane Collaboration, they can provide quick access to valid, summarized research evidence, including some unpublished “grey literature”.7
2. “Indexing type” bibliographical databases can be used to locate both primary and secondary published literature. The indexing system usually provides bibliographical information indexed by topic and allows the user to view citation details and the abstract of the published manuscript. They are normally searched as electronic databases.
7 The “grey” or unpublished literature can provide useful information because it often shows lack of superiority of newer medicines or other negative findings. Systematic reviews will seek out all scientifically sound studies and include “grey literature” to obtain a comprehensive evaluation.