NAT has emerged as the preferred method for the rapid diagnosis of CMV in immunocompromised hosts. In principle, the NAT assays are based on the detection and/or amplification of CMV nucleic acids in clinical samples. However, CMV persists in latent form in many nucleated cells; therefore, NAT has the risk of detect- ing inactive nonreplicating CMV. Generally, molecu- lar methods have higher sensitivity than nonmolecular methods. Among them, CMV PCR is the most widely used methodology. The basic principle of the CMV PCR is to generate a large number of target CMV gene-se- quence copies that can be easily detected.