PTGS1 and myocardial infarction: To demonstrate the usefulness of validated candidate reference genes in RT-qPCR, the expression level of cyclo-oxygenase 1 (COX-1) gene transcript in platelets of patients with the history of myocardial infarction, relative to its expression in a control, was investigated, using the least stable gene (OAZ1) and the three most stable reference genes for normalization (Figure 2A,B).