Given that we have begun to witness the application of associated genetic variants to disease prognosis [42],[43] and thus far we have convincing evidence for three RA-predisposing loci in our studies (HLA-DRB1, PTPN22 and the TRAF1 region), we estimated the risk of RA given genotypes at these three loci under three different possible unconditional RA risk assumptions (i.e. RA disease prevalence values) using Bayes' theorem. Here, PTPN22 is linked to rheumatoid arthritis.