Cited by 251Genetic Associations and EpidemiologyAdvanced Causal Inference TechniquesMeta-analysis and systematic reviews

Invited Commentary: Detecting Individual and Global Horizontal Pleiotropy in Mendelian Randomization-A Job for the Humble Heterogeneity Statistic?

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Bowden, Jack, Hemani, Gibran, Davey Smith, George·2018·American Journal of Epidemiology

Abstract

Mendelian randomization (MR) is gaining in recognition and popularity as a method for strengthening causal inference in epidemiology by utilizing genetic variants as instrumental variables. Concurrently with the explosion in empirical MR studies, there has been the steady production of new approaches for MR analysis. The recently proposed "global and individual tests for direct effects" (GLIDE) approach fits into a family of methods that aim to detect horizontal pleiotropy-at the individual single nucleotide polymorphism level and at the global level-and to adjust the analysis by removing outlying single nucleotide polymorphisms. In this commentary, we explain how existing methods can (and indeed are) being used to detect pleiotropy at the individual and global levels, although not explicitly using this terminology. By doing so, we show that the true comparator for GLIDE is not MR-Egger regression (as Dai et al., the authors of the accompanying article (Am J Epidemiol. 2018;187(12):2672-2680), claim) but rather the humble heterogeneity statistic.

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  • The study addressed bias from pleiotropic variants by considering heterogeneity in MR estimates from different instrument SNPs and by using weighted median MR sensitivity analysis.

    “which we addressed by considering the heterogeneity in the MR estimates produced by our different instrument SNPs [27,43] and in statistical sensitivity analysis using the weighted median MR approach, which is more robust to the inclusion of pleiotropic variants [29].”
  • In a one-sample setting with individual-level data, a causal effect estimate can be obtained using the two-stage least-squares (2SLS) method.

    “In a one-sample setting with individual-level data, a causal effect estimate can be obtained using the two-stage least-squares (2SLS) method.”

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Authors
Bowden, J., Hemani, G., & Davey Smith, G.
Affiliations
  • University of Bristol (GB)
  • MRC Integrative Epidemiology Unit, University of Bristol, Bristol, United Kingdom
Corresponding author
Bowden, Jack
Venue
American Journal of Epidemiology
Published
2018-09-05
Volume
187
Issue
12
Pages
2681-2685
ISSN
  • 0002-9262 (ISSN-L)
  • 1476-6256
OpenAlex
W2891812515
Cited by
251
References
28
Citations by year
2026: 8 · 2025: 36 · 2024: 84 · 2023: 35 · 2022: 27 · 2021: 21 · 2020: 26 · 2019: 14
Type
journal article
Language
en
Open access
Locations
  • American Journal of Epidemiology (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Bristol Research (University of Bristol) (submittedVersion, cc-by)
  • Explore Bristol Research (submittedVersion, cc-by)
Funders
Medical Research Council (MC_UU_00011/2, MC_UU_00011/1)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetic Associations and Epidemiology
  • Physical Sciences › Mathematics › Statistics and Probability › Advanced Causal Inference Techniques
  • Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
Keywords
horizontal pleiotropy, Mendelian randomization, glides, instrumental variable validity, causal inference
MeSH terms
Polymorphism, Single Nucleotide, Mendelian Randomization Analysis

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