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. 2004 Jul 13:4:18.
doi: 10.1186/1471-2288-4-18.

Evaluating heterogeneity in cumulative meta-analyses

Elmer V Villanueva  1 , Silva Zavarsek
Affiliations

Evaluating heterogeneity in cumulative meta-analyses

Elmer V Villanueva et al. BMC Med Res Methodol. .

Abstract

Background: Recently developed measures such as I2 and H allow the evaluation of the impact of heterogeneity in conventional meta-analyses. There has been no examination of the development of heterogeneity in the context of a cumulative meta-analysis.

Methods: Cumulative meta-analyses of five smoking cessation interventions (clonidine, nicotine replacement therapy using gum and patch, physician advice and acupuncture) were used to calculate I2 and H. These values were plotted by year of publication, control event rate and sample size to trace the development of heterogeneity over these covariates.

Results: The cumulative evaluation of heterogeneity varied according to the measure of heterogeneity used and the basis of cumulation. Plots produced from the calculations revealed areas of heterogeneity useful in the consideration of potential sources for further study.

Conclusion: The examination of heterogeneity in conjunction with summary effect estimates in a cumulative meta-analysis offered valuable insight into the evolution of variation. Such information is not available in the context of conventional meta-analysis and has the potential to lead to the development of a richer picture of the effectiveness of interventions.

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Figures

Figure 1
Figure 1
Cumulative meta-analytic estimates of the odds ratio (OR) for clonidine, nicotine replacement therapy (gum and patch), physician advice and acupuncture as smoking cessation interventions across time are shown in the first row of graphs. The second row outlines the development of Cochrane's Q. The last row describes the trends in I2. All analyses were cumulated by publication date.
Figure 2
Figure 2
A comparison between trends in I2 (first row) and H (second row) across time for smoking cessation interventions.
Figure 3
Figure 3
Trends in the summary odds ratio (OR) and I2 for nicotine replacement therapy using gum. The first column shows trends by year of publication, the second by control event rate, and the last by cumulative sample size.
See this image and copyright information in PMC

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