Test ID: CMM    
Cytomegalovirus (CMV) Antibodies, IgM, Serum

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

Cytomegalovirus (CMV) is a significant cause of morbidity and mortality, especially in organ transplant recipients and individuals with AIDS. (1,2) CMV is also responsible for congenital disease of the newborn. The most common infections with CMV in immunocompromised hosts result from reactivation of the virus (latent) from a previous infection, transmission of the virus from a donor organ or blood product, or initial or primary contact with the virus in a seronegative patient. Infection in immunologically normal patients can cause mononucleosis similar to that produced by infection with Epstein-Barr virus (EBV).

Negative (reported as positive or negative) 

The presence of IgM class antibodies indicates recent infection.

Negative cytomegalovirus (CMV) IgM results suggest that an individual 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 antibody was 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 post-infection. 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.

Positive test results may not be valid in persons who have received blood transfusions or other blood products in the past several months.

IgM responses can vary from patient to patient. A negative result does not preclude the possibility of recent primary cytomegalovirus (CMV) infection.

Serum specimens with total IgG concentrations of > or =20 mg/mL may cause interference in the CMV IgM assay.

Results must be used in conjunction with clinical symptoms and patient history.

A specimen taken late, after the convalescent stage of infection, may not contain detectable levels of IgM antibodies to CMV. Because CMV IgM antibody may persist for many months after primary infection, its detection in a single serum specimen is of limited value in determining the timing when infection occurred. Negative results do not preclude recent infection by CMV.

This test should not be used as a general screen in the absence of clinical symptoms or known exposure.

Epstein-Barr virus (EBV) is known to be a potent B-cell stimulator. Infections with EBV have been suspected to elicit antigen-specific IgM responses in individuals previously sensitized to a variety of non-EBV infectious agents.

1. Kusne S, Shapiro R, Fung J: Prevention and treatment of cytomegalovirus infection in organ transplant recipients. Transpl Infect Dis 1999;1(3):187-203

2. Rubin RH: Importance of CMV in the transplant population. Transpl Infect Dis 1999;1(1):3-7

3.Lang D, Vornhagen R, Rothe M, et al: Cross-reactivity of Epstein-Barr virus-specific immunoglobulin M antibodies with cytomegalovirus antigens containing glycine homopolymers. Clin Diagn Lab Immunol 2001 July;8(4):747-756