Interpretation

A negative cytomegalovirus (CMV) IgM result suggests that the patient is not experiencing acute or active 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, a few pregnant women, and kidney 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.