Cytomegalovirus (CMV) Antibodies, Qualitative, IgM

The CMV IgM antibody test (CMV IgM; anti-cytomegalovirus immediate early antibody) assists in diagnosing current or recent CMV infection. Because CMV IgM can persist for more than 12 months after infection and may be present with secondary infection or reactivation, isolated IgM reactivity does not confirm primary infection. IgG seroconversion on paired specimens provides the strongest serologic evidence for primary infection. For suspected acute disease, paired testing for CMV IgG and IgM two or more weeks apart is recommended, and nucleic acid amplification testing can identify active infection. Ordering is appropriate when evaluating suspected CMV disease in immunocompromised patients (eg, HIV infection, malignancy, or immunosuppressive therapy), during pregnancy to consider maternal primary infection risk, and in the diagnostic workup of possible congenital CMV infection.

CMV infection is prevalent worldwide; after primary infection the virus becomes latent, and loss of immune control permits reactivation that can lead to clinically significant disease in immunocompromised hosts. Transmission occurs through close contact with body fluids, sexual exposure, transplacental spread, and transfusion. Immunocompetent individuals are often asymptomatic or develop a mononucleosis-like illness, whereas patients with impaired immunity can experience organ-invasive disease such as pneumonia or hepatitis. Primary maternal infection early in pregnancy is associated with fetal infection and adverse outcomes. CMV-specific IgM arises early after infection and may also be present during reactivation; qualitative positive results reflect exceedance of the assay cutoff and are not proportional to antibody concentration.