Where is the evidence?

Issue: BCMJ, vol. 55, No. 9, November 2013, Page 437 College Library

Reviewing recent credible medi-cal studies is essential to the practice of evidence-based medicine, which may be defin-ed as “the integration of best research evidence with clinical expertise and patient values.”[1] A question that frequently arises at the College of Physicians and Surgeons of British Columbia library from doctors conducting searches to support their practice is, “What is the difference between a systematic review and a meta-analysis?”

Systematic reviews address a focused and answerable clinical question, have explicit search methodology, and attempt to examine the whole range of studies conducted on a particular clinical question. This ensures more reliable evidence than a standard narrative review article as the systematic review is comprehensive, grapples with ambiguities and conflicting results, and presents a bottom-line interpretation. Occasionally the conclusion reached is “not enough evidence is available to answer the question,” which may be a valuable conclusion in itself.

Meta-analyses merge the evidence found in studies considered in systematic reviews after managing such issues as heterogeneity between the studies. By analyzing this larger pool of evidence using statistical methods, more powerful conclusions may be drawn. In addition, inconclusive evidence and inconsistencies between studies may be examined in greater detail.

Well-designed systematic reviews and meta-analyses offer the highest levels of evidence on clinical questions and are found in various databases such as MEDLINE, Clinical Evidence, and the Cochrane Library. All of these databases are available for free to college registrants through the College Library (www.cpsbc.ca/library/search-materials/databases).
—Paula Osachoff
College Librarian


This article is the opinion of the Library of the College of Physicians and Surgeons of BC and has not been peer reviewed by the BCMJ Editorial Board.


1.    Understanding systematic reviews and meta-analysis. Archives of Disease in Childhood 2005;90:845-848.

Paula Osachoff. Where is the evidence?. BCMJ, Vol. 55, No. 9, November, 2013, Page(s) 437 - College Library.

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