What is the Difference Between CMV IgG and IgM?

The main difference between CMV IgG and IgM lies in their presence and behavior during different stages of a Cytomegalovirus (CMV) infection. Here are the key differences:

1. IgM: Positive CMV IgM results indicate a recent infection (primary, reactivation, or reinfection). IgM antibodies are produced several weeks after the initial CMV infection and rise during the active infection. A positive CMV IgM and negative IgG means you may have very recently been infected. IgM antibodies may remain positive for over 4 months (sometimes up to a year or more).
2. IgG: Positive CMV IgG results indicate past or recent CMV infection. IgG antibodies are produced several weeks after the initial CMV infection and rise during the active infection, then stabilize as the CMV infection resolves and the virus becomes inactive. A high level of IgG is not as important as a rising level. If there is a 4-fold increase in IgG between the first and second sample, then you have an active CMV infection (primary or reactivated).

In summary, CMV IgM is associated with recent infections, while CMV IgG is associated with past or recent infections. Combining the results of both tests can help determine the timing and status of a CMV infection.

Comparative Table: CMV IgG vs IgM

Here is a table summarizing the differences between CMV IgG and IgM:

In summary, CMV IgG and IgM are two types of antibodies produced by the body against Cytomegalovirus (CMV). CMV IgG is produced several weeks after the primary infection and remains detectable throughout the lifetime, providing protection against reinfection. In contrast, CMV IgM is produced as a first response to primary infection and gradually decreases and becomes undetectable after 4 months. The presence of CMV IgG indicates past exposure to CMV or latent infection, while the presence of CMV IgM along with IgG indicates primary infection or reactivation of latent infection.