[R] How to interpret Mendelian randomization results?

[Ana Marija]

Hello,

I did Mendelian randomization using this software:
https://cran.r-project.org/web/packages/MendelianRandomization/vignettes/Vignette_MR.pdf

library(MendelianRandomization)
f=read.table("246LDout272Biobank_Retina.txt", header=T)
> head(f)
          rs exposure.beta exposure.se outcome.beta outcome.se
1  rs1029830      0.723525  0.03026430  0.066715400  0.0359278
2  rs1029832      0.723785  0.03029603  0.064105600  0.0359021
3 rs11078374     -0.411789  0.04189295 -0.000376929  0.0406439
4 rs11078382      0.882549  0.14275799 -0.197074000  0.1247720
5  rs1124961     -0.333763  0.05589377 -0.075468600  0.0576012
6  rs1135237     -0.316831  0.05552530 -0.074086200  0.0573111

MRInputObject <- mr_input(bx = f$exposure.beta,bxse = f$exposure.se,by
= f$outcome.beta,byse = f$outcome.se)
EggerObject <- mr_egger(MRInputObject,robust = FALSE,penalized =
FALSE,correl = FALSE,distribution = "normal",alpha = 0.05)

MR-Egger method
(variants uncorrelated, random-effect model)

Number of Variants =  246

------------------------------------------------------------------
  Method     Estimate Std Error  95% CI       p-value
  MR-Egger    0.115     0.016  0.084, 0.146   3.28e-13
 (intercept) -0.010     0.008 -0.025, 0.006   0.226
------------------------------------------------------------------
Residual Standard Error :  1.106
Heterogeneity test statistic = 298.4508 on 244 degrees of freedom,
(p-value = 0.0099)
 I^2_GX statistic: 97.2%

Let's say that my exposure is called Retina and my outcome is called
Biobank. Can someone please help me interpret these results in terms
of 'horizontal pleiotropy' as mentioned here:
https://www.ncbi.nlm.nih.gov/pubmed/29771313


Thanks
Ana