Dear all,

I am trying to calculate PGS in a twin sample and I have some questions about how to proceed.

1-my first question is about the Base Data. I thought that in order to calculate PGS we need summary statistics from a GWAS (ideally the largest GWAS). However, I have seen the PGI repository (https://www.thessgac.org/pgi-repository). I am not sure what kind of data is stored there. Are data from GWAS studies or PGS studies? If the latter, how they extract summary statistics? Is there any difference of using data from the PGI repository or from the largest GWAS?

2-what is the best method to treat twin pairs? Should I split the sample into two independent samples? Or should I analyse the whole sample and account for relatedness? How can I account for the relatedness among twin pairs?

Thank you so much in advance.