In the field of transplantation, CMV serology is performed on blood samples from the prospective organ donor and recipient to determine the risk of primary infection or reactivation of disease. The knowledge of these risks influences the type of preventive efforts for each patient population. Specifically, a CMV D+/R- mismatch SOT recipient has the highest risk of primary CMV disease, and therefore may benefit from antiviral prophylaxis or aggressive CMV surveillance and pre- emptive therapy. Some centers have also used serology to determine ongoing risk of primary CMV disease after transplantation since seroconversion would suggest pro- tection from subsequent CMV disease