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Sensitivity of between-study heterogeneity in meta-analysis: proposed metrics and empirical evaluation

Open access
Patsopoulos, Nikolaos A, Evangelou, Evangelos, Ioannidis, John PA·2008·International Journal of Epidemiology

Abstract

BACKGROUND: Several approaches are available for evaluating heterogeneity in meta-analysis. Sensitivity analyses are often used, but these are often implemented in various non-standardized ways. METHODS: We developed and implemented sequential and combinatorial algorithms that evaluate the change in between-study heterogeneity as one or more studies are excluded from the calculations. The algorithms exclude studies aiming to achieve either the maximum or the minimum final I(2) below a desired pre-set threshold. We applied these algorithms in databases of meta-analyses of binary outcome and >/=4 studies from Cochrane Database of Systematic Reviews (Issue 4, 2005, n = 1011) and meta-analyses of genetic associations (n = 50). Two I(2) thresholds were used (50% and 25%). RESULTS: Both algorithms have succeeded in achieving the pre-specified final I(2) thresholds. Differences in the number of excluded studies varied from 0% to 6% depending on the database and the heterogeneity threshold, while it was common to exclude different specific studies. Among meta-analyses with initial I(2) > 50%, in the large majority [19 (90.5%) and 208 (85.9%) in genetic and Cochrane meta-analyses, respectively] exclusion of one or two studies sufficed to decrease I(2) < 50%. Similarly, among meta-analyses with initial I(2) > 25%, in most cases [16 (57.1%) and 382 (81.3%), respectively) exclusion of one or two studies sufficed to decrease heterogeneity even <25%. The number of excluded studies correlated modestly with initial estimated I(2) (correlation coefficients 0.52-0.68 depending on algorithm used). CONCLUSIONS: The proposed algorithms can be routinely applied in meta-analyses as standardized sensitivity analyses for heterogeneity. Caution is needed evaluating post hoc which specific studies are responsible for the heterogeneity.

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Cited by

Metadata

Authors
Patsopoulos, N. A., Evangelou, E., & Ioannidis, J. P.
Venue
International Journal of Epidemiology
Published
2008-04-18
Volume
37
Issue
5
Pages
1148-1157
ISSN
  • 0300-5771 (ISSN-L)
  • 1464-3685
OpenAlex
W2112970335
Cited by
1,138
References
8
FWCI
12.74
Type
journal article
Language
en
Open access
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