MR-GRIP: a modified MR-Egger model with the Genotype Recoding Invariance Property

This implements the modified MR-Egger model with the Genotype Recoding Invariance Property (MR-GRIP) due to Dudbridge and Bowden et al. (2025). It is well known that the results of MR-Egger are sensitive to which alleles are designated as the effect alleles. A pragmatic convention is to orient all SNPs to have positive effects on the exposure, which has some advantages in interpretation but also brings some philosophical limitations. The MR-GRIP model is a modification to the MR-Egger model in which each term is multiplied by the genotype-phenotype associations. This makes each term in the model invariant to allele coding.

Usage

mr_grip(b_exp, b_out, se_exp, se_out, parameters)

Arguments

b_exp

Vector of genetic effects on exposure.

b_out

Vector of genetic effects on outcome.

se_exp

Standard errors of genetic effects on exposure.

se_out

Standard errors of genetic effects on outcome.

parameters

List of parameters.

Value

List of with the following elements:

b

MR estimate

se

Standard error of MR estimate

pval

p-value of MR estimate

Q, Q_df, Q_pval

Heterogeneity stats

b.wi

MR estimate adjusting for weak instruments

se.wi

Standard error adjusting for weak instruments

pval.wi

p-value adjusting for weak instruments

mod

Summary of regression

dat

Original data used for MR-GRIP