Shortly after infection with CMV, humoral and cellular responses to CMV can be detected. Serologic testing for IgG and IgM antibodies to CMV are helpful clinically in distinguishing acute from previous infections. They are 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. In Kansas City only 25% of healthy persons, age 18-23 years, are seropositive, compared to 89% of adults 60 years or older. Females have a higher antibody prevalence than males in each age group. 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 in primary infections in uncompromised patients 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. Within two to three weeks after the onset of clinical symptoms, CMV IgG antibodies can be detected. The IgG response is persistent and levels remain fairly constant throughout the patient's lifetime. In atypical cases, IgM may persist or reappear. Reinfection or reactivation of a latent infection is usually responsible for reappearance of IgM.
Interpretation |
IgM |
IgG |
Uninfected, seronegative |
Negative |
Negative |
Acute infection |
Positive |
Negative |
Recent infection |
Positive |
Positive |
Reactivation |
Positive |
Positive |
Past Infection |
Negative |
Positive |
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.
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