In our study, we calculated the overall interaction (i.e., due to all 2- and 3-way interactions) between HLA-DRB1*15, absence of HLA-A*02, and organic solvents with regard to MS risk, by comparing the joint effect of the 3 risk factors to the situation when each one acts separately, using the TotAP. Here, HLA-DRB1 is linked to myeloid sarcoma.