Cytomegalovirus Antibody

Cytomegalovirus Antibody

Cytomegalovirus (CMV) is a member of the Herpesviridae family of viruses and usually causes asymptomatic infection after which it remains latent in patients, primarily within bone marrow derived cells. Primary CMV infection in immunocompetent individuals may manifest as a mononucleosis-type syndrome, similar to primary Epstein-Barr virus infection, with fever, malaise and lymphadenopathy.

CMV is a significant cause of morbidity and mortality among bone marrow or solid organ transplant recipients, individuals with AIDS, and other immunosuppressed patients. They can become ill from a newly acquired primary infection or by virus reactivation. CMV also infect newborns and is classified as one of the TORCH infections (toxoplasmosis, other infections including rubella, CMV, and herpes simplex virus).

Shortly after infection with cytomegalovirus (CMV), humoral and cellular responses can be detected. Serologic testing for IgG and IgM antibodies to CMV is helpful clinically in distinguishing acute from previous infections. It also useful in determining the CMV antibody status of transplant candidates.  

CMV antibody prevalence varies directly with age, geographical region, and socioeconomic class.  CMV IgG can be detected in 40 to 79% of healthy adults in developed countries and 80 to100% of adults in developing countries. In developed countries, infection is often delayed until adulthood. The majority of immunocompetent adults have demonstrable levels of CMV IgG. To diagnose an acute infection it is necessary to test for CMV IgM antibodies. Acute and convalescent samples can be compared for evidence of rising CMV IgG levels and declining IgM levels.  

The antibody response to primary infections in patients who are immunocompetent typically involves an initial rise in IgM, followed by a rise in IgG. The IgM antibody appears within the first 10 days after infection and persists for up to 16 weeks. In atypical cases, IgM may persist or reappear. Reinfection or reactivation of a latent infection is usually responsible for reappearance of IgM.  

A negative result for CMV IgM usually suggests the patient does not have an acute infection. However, some infants and pregnant women may not have detectable CMV IgM. Positive CMV IgM results indicate a recent infection either due to primary infection, reinfection, or reactivation.

Within two to three weeks after the onset of clinical symptoms, CMV IgG antibodies can be detected. A positive CMV IgG result indicates either a past or recent infection. A negative CMV IgG result suggests a person has not had prior exposure to CMV. The IgG response is persistent and levels remain fairly constant throughout the patient's lifetime.

Specimen requirement is one SST tube of blood.  Sera are stored frozen in the laboratory for 3 months for paired serum testing.  Specimens are stored indefinitely for transplant candidates.  Serial specimens should be collected at 2, 4, and 8 week intervals after disease onset.

References

Staras SA, et al. Seroprevalence of cytomegalovirus infection in the United States, 1998-1994. Clin Infect Dis. 2006;43(9):1143-1151.

Humar A, et al. Clnical Utility of Cytomegalovirus (CMV) Serology Testing in High-risk CMV D_/R- Transplant Recipients, Amer J Transplant 2005;5:1065-1070.

Chan ES, et al. Maternal Cytomegalovirus (CMV) Serology: The Diagnostic Limitations of CMV IgM and IgG Avidity in Detecting Congenital CMV Infection. Pediatric and Developmental Pathology. 2024;27(6):530-544