BMJ 1997;315:1533-1537 (6 December)

Education and debate

Meta-analysis: Principles and procedures

Matthias Egger, reader in social medicine and epidemiology,a George Davey Smith, professor of clinical epidemiology,a Andrew N Phillips, professor of epidemiology and biostatistics,b  This is the second in a series of seven articles examining the procedures in conducting reliable meta-analysis in medical research

a Department of Social Medicine, University of Bristol, Bristol BS8 2PR, b Department of Primary Care and Population Sciences, Royal Free Hospital School of Medicine, London NW3 2PF

Correspondence to: Dr Eggerm egger@bristol.ac.uk


right arrow   Introduction

Meta-analysis is a statistical procedure that integrates the results of several independent studies considered to be "combinable."1 Well conducted meta-analyses allow a more objective appraisal of the evidence than traditional narrative reviews, provide a more precise estimate of a treatment effect, and may explain heterogeneity between the results of individual studies.2 Ill conducted meta-analyses, on the other hand, may be biased owing to exclusion of relevant studies or inclusion of inadequate studies.3 Misleading analyses can generally be avoided if a few basic principles are observed. In this article we discuss these principles, along with the practical steps in performing meta-analysis.


right arrow   Observational study of evidence

Meta-analysis should be viewed as an observational . . . [Full text of this article]

Summary points


right arrow   Standardised outcome measure
Odds ratio or relative risk?


right arrow   Statistical methods for calculating overall effect

right arrow   Bayesian meta-analysis

right arrow   Heterogeneity between study results

right arrow   Graphic display

right arrow   Relative and absolute measures of effect

right arrow   Sensitivity analysis

right arrow   Conclusions

right arrow   Acknowledgements

right arrow   Notes

right arrow   References

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