Question 30

a) What is a meta-analysis?

b) What is the role of meta-analysis in evidence based medicine?

c) What are the features you look for in a meta-analysis to determine if it has been well conducted?

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College Answer

a)  A form of systematic review that uses statistical methods to combine the results from different studies

b)  roles:


↑ statistical power by ↑ sample size


Resolve uncertainty when studies disagree


Improve estimates of effect size


Establish questions for future PRCTs



Are the research questions defined clearly?


Are the search strategy and inclusion criteria described?


How did they assess the quality of studies?


Have they plotted the results?


Have they inspected the data for heterogeneity?


How have they calculated a pooled estimate?


Have they looked for publication bias?


This question - though not entirely identical - is very similar to Question 5 from the second paper of 2013. The key difference is the inclusion of the nebulous question about the role of meta-analysis in EBM. In the later paper, this was focused specifically on the advantages of meta-analysis over the analysis of a single study. If one compares the above answer to (b) with the answer (b) in Question 5, one will discover similarities, which suggests that the college was looking for a list of advantages here as well.

Thus, much of the below is a direct copy of Question 5.

a) What is a meta-analysis?

Meta-analysis is a tool of quantitative systematic review.

It is used to weigh the available evidence from RCTs and other studies based on the numbers of patients included, the effect size, and on statistical tests of agreement with other trials.

b) What is the role of meta-analysis  in evidence based medicine?

  • It offers an objective quantitative appraisal of evidence
  • It reduces the probability of false negative results
  • The combination of samples leads to an improvement of statistical power
  • Increased sample size may increase the accuracy of the estimate
  • It may explain heterogeneity between the results of different studies
  • Inconsistencies among trials may be quantified and analysed

c) What are the features you look for in a meta-analysis to determine if it has been well conducted?

  • Research questions clearly defined
  • Transparent search strategy
  • Thorough search protocol
  • Authors contacted and unpublished data collected
  • Definition of inclusion and exclusion criteria for studies
  • Sensible exclusion and inclusion criteria
  • Assessment of methodological quality of the included studies
  • Transparent methodology of assessment
  • Calculation of a pooled estimate
  • Plot of the results (Forest Plot)
  • Measurement of heterogeneity
  • Assessment of publication bias (Funnel Plot)
  • Reproduceable meta-analysis strategy (eg. multiple reviewers perform the same meta-analysis, according to the same methods)


Sauerland, Stefan, and Christoph M. Seiler. "Role of systematic reviews and meta-analysis in evidence-based medicine." World journal of surgery 29.5 (2005): 582-587.


DerSimonian, Rebecca, and Nan Laird. "Meta-analysis in clinical trials."Controlled clinical trials 7.3 (1986): 177-188.


Rockette, H. E., and C. K. Redmond. "Limitations and advantages of meta-analysis in clinical trials." Cancer Clinical Trials. Springer Berlin Heidelberg, 1988. 99-104.


Walker, Esteban, Adrian V. Hernandez, and Michael W. Kattan. "Meta-analysis: Its strengths and limitations." Cleveland Clinic Journal of Medicine75.6 (2008): 431-439.


Methodological Expectations of Cochrane Intervention Reviews