Cytomegalovirus (CMV) Antibody, IgG

The Cytomegalovirus (CMV) Antibody, IgG test (Anti‑CMV IgG) is used to confirm previous CMV exposure and immune status and to aid in diagnosing CMV infection in the appropriate clinical context. It also assists in differentiating CMV from other causes of a mononucleosis‑like illness when Epstein–Barr virus studies are negative. In pregnancy, CMV IgG is interpreted together with CMV IgM and CMV IgG avidity to estimate the timing of maternal infection and to frame the risk of congenital CMV. In immunocompromised individuals, serology is evaluated in conjunction with molecular results and clinical findings.

Cytomegalovirus is a human herpesvirus that establishes lifelong latency with the potential to reactivate. Primary infection in immunocompetent persons is commonly asymptomatic or presents as a mononucleosis‑like illness. Transmission occurs through saliva, urine, blood, and semen, and vertically from mother to child in utero, during delivery, or through breastfeeding. Primary maternal infection during pregnancy carries the highest risk for congenital CMV, which occurs in a subset of infections and may result in microcephaly, intracranial calcifications, hepatosplenomegaly, rash, sensorineural hearing loss, neurodevelopmental impairment, or fetal demise. Severe disease can occur in the setting of immunodeficiency, including retinitis, colitis, esophagitis, and encephalitis. CMV‑specific IgG appears within weeks after a primary infection and then persists; assessment of IgG avidity helps distinguish recent primary infection (low avidity) from past infection or reactivation (high avidity).