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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.(1) Primary CMV infection in immunocompetent individuals may also 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 due to virus reactivation or from a newly acquired infection.(2,3) Infection in these patient populations can affect almost any organ and lead to multiorgan failure. CMV is also responsible for congenital disease among newborns and is 1 of the TORCH infections (toxoplasmosis, other infections including syphilis, rubella, CMV, and herpes simplex virus).
CMV seroprevalence increases with age. In the United States the prevalence of CMV specific antibodies increases from approximately 36% to over 91% in adolescents between the ages of 6 to 11 and adults over 80 years old, respectively.(4)
Diagnosis of primary, acute phase infection with cytomegalovirus (CMV), especially in patients with infectious mononucleosis and pregnant women who, based on clinical signs or exposure, may have primary CMV infection
A negative cytomegalovirus (CMV) IgM results suggest that the patient is not experiencing a recent infection. However, a negative result does not rule-out primary CMV infection.
It has been reported that CMV-specific IgM antibodies were not detectable in 10% to 30% of cord blood sera from infants demonstrating infection in the first week of life. In addition, up to 23% (3/13) of pregnant women with primary CMV infection did not demonstrate detectable CMV IgM responses within 8 weeks postinfection. In cases of primary infection where the time of seroconversion is not well defined as high as 28% (10/36) of pregnant women did not demonstrate CMV-IgM antibody.
Positive CMV IgM results indicate a recent infection (primary, reactivation, or reinfection).
IgM antibody responses in secondary (reactivation) CMV infections have been demonstrated in some CMV mononucleosis patients, in a few pregnant women, and in renal and cardiac transplant patients. Levels of antibody may be lower in transplant patients with secondary, rather than primary, infections.
Equivocal CMV IgM results may occur during acute infection or may be due to nonspecific binding reactions. Submit an additional sample for testing if clinically indicated.
Sera drawn very early during the acute stage of infection may have undetectable levels of cytomegalovirus (CMV) IgM.
Immunocompromised patients may have impaired immune responses and nonreactive IgM results may be due to delayed seroconversion and do not rule-out current infection.
CMV IgM results should not be used alone to diagnose CMV infection. Results should be considered in conjunction with clinical presentation, patient history, and other laboratory findings. In cases of suspected disease, submit a second sample for testing in 10 to 14 days.
The performance characteristics of these assays have not been evaluated in immunosuppressed or organ transplant recipients and have not been established for cord blood or for testing of neonates. These assays should not be used for screening blood or plasma donors.
Immune complexes or other immunoglobulin aggregates present in patient samples may cause increased nonspecific binding and produce false-positive results.
Potential cross-reactivity for CMV IgM may occur with specimens positive for Epstein-Barr virus VCA IgM and parvovirus B19 IgM.
Negative (Reported as positive, negative, or equivocal)
1. Soderberg-Naucler C, Khanna R, et al: Reactivation of latent human cytomegalovirus by allogeneic stimulation of blood cells from healthy donors. Cell 1997;91:119
2. Kusne S, Shapiro R, Fung J: Prevention and treatment of cytomegalovirus infection in organ transplant recipients. Transpl Infect Dis 1999;1(3):187-203
3. Rubin RH: Importance of CMV in the transplant population. Transpl Infect Dis 1999;1(1):3-7
4. Staras SA, Dollard SC, Radford KW, et al: Seroprevalence of cytomegalovirus infection in the United States, 1998-1994. Clin Infect Dis 2006;43(9):1143