Cytomegalovirus Antibody, IgG Avidity

Use

Identifying CMV infections in pregnant women during the first trimester is of significant importance for clinical care. Acute infection is typically characterized by increased CMV-specific IgM and IgG antibodies. However, CMV IgM antibodies may persist for several months or even years after initial infection, which limits their utility in the accurate diagnosis of recent CMV infection. CMV IgM antibodies can also be detected during viral reactivation, complicating the diagnosis of a recent primary infection. Measuring IgG antibody avidity to CMV antigens can aid in discriminating recent from prior CMV infections. Index values of 0.5 or less generally indicate recent infection (within the previous 3 to 4 months). Low avidity values cannot exclude persistent IgG antibodies with low avidity. Index values of 0.6 or greater indicate an infection occurring more than 3 months prior to testing. Detection of high avidity CMV IgG antibodies during the first trimester (12 to 16 weeks gestation) helps exclude a diagnosis of acute CMV infection post-conception.