Title



     mreggersimex -- SIMEX for the MR-Egger estimator



Syntax



        mreggersimex varname_gd varname_gp [aweight] [if] [in] [, options]



    options                 Description
    ----------------------------------------------------------------------------------------------
      mreggeropts           Options for mregger
      bsopts                Options for bootstrap
      gxse(varname)         Variable containg genotype-phenotype (SNP-exposure) SEs
      noboot                Do not perform bootstrapping for SEs
      nodraw                Do not draw SIMEX plot
      reps(#)               No. bootstrap replications
      seed(#)               Seed for random number generator, specify for reproducible results
      simreps(#)            No. simulation replications



Description



    mreggersimex performs the simulation extrapolation (SIMEX) algorithm (Cook et al., 1995,
    Hardin et al., 2003) on mregger using the commonly applied quadratic extrapolation (Bowden et
    al., 2016).



    varname_gd variable containing the genotype-disease (SNP-outcome) association estimates.



    varname_gp variable containing the genotype-phenotype (SNP-exposure) association estimates.



    For the analytic weights you need to specify the inverse of the genotype-disease (SNP-outcome)
    SEs squared, i.e. aw=1/(gdse^2).



Examples



    Using the data provided by Do et al. (2013) recreate Bowden et el. (2016), Figure 4, LDL-c
    "All genetic variants" (plot in row 2, column 1).



    Setup
        . use https://raw.github.com/remlapmot/mrrobust/master/dodata, clear



    Select observations (p-value with exposure < 10^-8)
        . gen byte sel1 = (ldlcp2 < 1e-8)



    SIMEX using default settings
        . mreggersimex chdbeta ldlcbeta [aw=1/chdse^2] if sel1==1, gxse(ldlcse) seed(12345)



    Suppressing the bootstrap SEs
        . mreggersimex chdbeta ldlcbeta [aw=1/chdse^2] if sel1==1, gxse(ldlcse) seed(12345) noboot



    Suppressing the bootstrap SEs and the plot
        . mreggersimex chdbeta ldlcbeta [aw=1/chdse^2] if sel1==1, gxse(ldlcse) seed(12345) noboot
            nodraw



References



    Bowden J, Del Greco FM, Minelli C, Davey Smith G, Sheehan NA, Thompson JR.  Assessing the
        suitability of summary data for two-sample Mendelian randomization analyses using MR-Egger
        regression: the role of the I2 statistic.  International Journal of Epidemiology, 2016,
        45, 6, 1961-1974.  DOI



    Bowden J, Davey Smith G, Haycock PC, Burgess S.  Consistent estimation in Mendelian
        randomization with some invalid instruments using a weighted median estimator. Genetic
        Epidemiology, 2016, 40, 4, 304-314.  DOI



    Cook J and Stefanski LA. A simulation extrapolation method for parametric measurement error
        models. Journal of the American Statistical Association, 1995, 85, 652-663.  Link



    Do R et al. Common variants associated with plasma triglycerides and risk for coronary artery
        disease. Nature Genetics, 2013, 45, 1345-1352. DOI:  DOI



    Hardin JW, Schmiediche H, Carroll RJ. The simulation extrapolation method for fitting linear
        models with additive measurement error. Stata Journal.  2003, 3, 4, 373-385.  DOI



Author



INCLUDE help mrrobust-author