Systematic reviews in health care: Assessing the quality of controlled clinical trials

doi:10.1136/bmj.323.7303.42

BMJ 2001;323:42-46 ( 7 July )

Education and debate

Systematic reviews in health care

Assessing the quality of controlled clinical trials

This is the first in a series of four articles

Peter Jüni, research fellow ^a, Douglas G Altman, professor of statistics in medicine ^b, Matthias Egger, senior lecturer in epidemiology and public health medicine ^c.

^a Department of Social and Preventive Medicine, University of Bern, Bern, 3012 Switzerland, ^b Imperial Cancer Research Fund Medical Statistics Group, Centre for Statistics in Medicine, Institute of Health Sciences, Oxford OX3 7LF, ^c Medical Research Council Health Services Research Collaboration, Department of Social Medicine, University of Bristol, Bristol BS8 2PR

Correspondence to: M Egger m.egger@bristol.ac.uk

The first 150 words of the full text of this article appear below.

The quality of controlled trials is of obvious relevance to systematic reviews. If the "raw material" is flawed then the conclusionsof systematic reviews cannot be trusted. Many reviewers formallyassess the quality of primary trials by following the recommendationsof the Cochrane Collaboration and other experts. ¹ ² However,the methodology for both the assessment of quality and its incorporationinto systematic reviews and meta-analysis are a matter of ongoingdebate.^3-5 In this article we discuss the concept of study qualityand the methods used to assess quality.

Table Removed (Available Only in the Full Text)

Quality is a multidimensional concept, which could relate to the design, conduct, and analysis of a trial, its clinical relevance,or quality of reporting.⁶ The validity of the findings generatedby a study clearly is an important dimension of quality. In the1950s the social scientist Campbell proposed a useful distinctionbetween internal and external validity (see box below). ⁷ ⁸ Internal validity implies that . . . [Full text of this article]

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Rapid Responses:

Read all Rapid Responses

Bias against quality scales: Terry P Klassen
bmj.com, 9 Jul 2001 [Full text]
Authors� response: Why scales are unhelpful for assessing quality of trials: Peter J�ni
bmj.com, 24 Aug 2001 [Full text]
Effect of intra and inter-observer variation on systematic reviews of controlled clinical trials: J Bernades, et al.
bmj.com, 5 Sep 2001 [Full text]