I have a twin dataset with proband ascertainment (i.e. at least one proband in each pair is affected). I cant seem to figure out how in incorporate this in my ACE model - can anyone help? I have found several examples involving ACE models in twin data (for example http://openmx.psyc.virginia.edu/svn/tags/stable-1.2/demo/UnivariateTwinAnalysis_PathRaw.R) however none of these speak of how to take proband ascertainment into account.
I have read that i read to include ascertainment probabilities, i.e. 0 for the healthy-healthy pairs (the ones i dont have), 1 for the concordant pairs and a free parameter between 0 and 1 for the disconcordant pairs. Does anyone know where to add this in the code and how??
I have read the manual on openmx and it didnt give me an answer..