Cytomegalovirus (CMV) Antibody, IgG

The Cytomegalovirus (CMV) Antibody, IgG test—also known as CMV IgG or Anti-CMV IgG—establishes CMV serostatus and evidence of past infection. In patients with compatible symptoms, results are interpreted with clinical findings and adjunctive studies such as CMV IgM or nucleic acid testing to assess suspected CMV infection. In preconception and prenatal care, CMV IgG assists in estimating the risk of congenital CMV and, when paired with IgG avidity testing or documented seroconversion, helps differentiate recent primary maternal infection from prior infection or reactivation. In immunocompromised populations, including transplant candidates/recipients and persons with advanced HIV, it supports baseline serostatus determination and risk stratification.

Cytomegalovirus is a human herpesvirus that establishes lifelong latency with the capacity for reactivation. Transmission occurs through body fluids and through vertical routes during pregnancy, delivery, or breastfeeding. In immunocompetent hosts, primary infection is frequently asymptomatic or presents as a mononucleosis-like syndrome, whereas severe disease is seen in immunocompromised individuals. Congenital CMV most often follows primary maternal infection and carries a risk of fetal infection. Among congenitally infected infants, a subset develops manifestations that include microcephaly, intracranial calcifications, hepatosplenomegaly, and sensorineural hearing loss. Following primary infection, CMV IgG levels rise within weeks and then persist. IgG avidity increases over months; low avidity supports recent primary infection, whereas high avidity is consistent with remote infection or reactivation. Serologic findings should be integrated with the clinical context and, when indicated, CMV IgM, nucleic acid testing, or other supporting assays.