It is interesting to note that when, by chance, a true positive result is found, as in the case for PTPN22 Arg620Trp SNP in type 1 diabetes [5], it is replicated by many groups, very rapidly [6,39,51,52], although this has a large effect approaching an OR = 2. The gene discussed is PTPN22; the disease is type 1 diabetes mellitus.