Maternal and congenital human cytomegalovirus infection: laboratory testing for detection and diagnosis

Human cytomegalovirus (CMV) is the leading cause of congenital infection worldwide and the most common cause of non-genetic sensorineural hearing loss. As there is no vaccine or other specific intervention to prevent congenital CMV infection, there is a need to identify maternal and congenital infections with sensitive and specific testing as early as possible. There is no widely accepted practice for screening during pregnancy or in all newborns for identification of possible cases of congenital CMV. Currently, screening during pregnancy is limited to those identified as at risk followed by fetal and/or neonatal testing when congenital infection is suspected. This review focuses primarily on the current status of laboratory testing for diagnosis of maternal and congenital CMV infections. Primary maternal infection is best diagnosed using serologic testing, including CMV IgM, IgG, and avidity testing, while fetal infection should be assessed by nucleic acid amplification testing (NAAT) of amniotic fluid. Urine and saliva NAATs are the mainstay for diagnosis of congenital CMV in the first 3 weeks of life. Testing of dried blood spots can be useful for diagnosis of congenital CMV outside of the newborn period. The gaps in knowledge such as the prognostic value of viral loads in various sample types are addressed.