Technical advanceStandard Reference Material 2366 for Measurement of Human Cytomegalovirus DNA

Human cytomegalovirus (CMV), classified as human herpesvirus 5, is ubiquitous in human populations. Infection generally causes little illness in healthy individuals, but can cause life-threatening disease in those who are immunocompromised or in newborns through complications arising from congenital CMV infection. An important aspect in diagnosis and treatment is to track circulating viral load with molecular methods, particularly with quantitative PCR. Standardization is vital, because of interlaboratory variability (due in part to the variety of assays and calibrants). Toward that end, the U.S. National Institute of Standards and Technology produced a Standard Reference Material 2366 appropriate for establishing metrological traceability of assay calibrants. This standard is composed of CMV DNA (TowneΔ147 bacterial artificial chromosome DNA). Regions of the CMV DNA that are commonly used as targets for PCR assays were sequenced. Digital PCR was used to quantify the DNA, with concentration expressed as copies per microliter. The materials were tested for homogeneity and stability. An interlaboratory study was conducted by Quality Control for Molecular Diagnostics (Glasgow, UK), in which one component of SRM 2366 was included for analysis by participants in a CMV external quality assessment and proficiency testing program.