CMV IgG (Cytomegalovirus IgG)

What is CMV IgG?

The CMV IgG test looks for IgG-class antibodies produced by the body against cytomegalovirus (CMV), a member of the herpesvirus family. CMV is a very common virus, and the great majority of adults encounter it at some point in their lives, often without noticing. In healthy people, the infection usually causes no symptoms or passes as a mild cold or a mononucleosis-like illness.

Once the virus has entered the body, it remains dormant (latent) for life and can reactivate during periods when immunity is weakened. IgG antibodies form a few weeks after the infection and can usually be detected in the blood for life. CMV can be transmitted through saliva, urine, breast milk, blood and sexual contact, or from mother to baby during pregnancy. The test is run on a serum sample using immunological methods such as ELISA or chemiluminescence.

When is the CMV IgG test ordered?

CMV IgG is ordered to determine whether a person has previously been exposed to this virus, and therefore their risk status. Especially in pregnancy, organ transplantation and immunosuppressed states, this information is important for planning prevention and monitoring. When an acute infection is suspected, it is usually evaluated together with CMV IgM.

• Immunity check, when the doctor considers it necessary, in women who are planning a pregnancy or are pregnant
• Evaluation of the donor and recipient before an organ or bone marrow transplant
• Risk assessment in immunocompromised patients, such as people receiving chemotherapy or living with HIV
• Mononucleosis-like symptoms such as prolonged fever, fatigue and swollen lymph nodes
• Selection of blood products to be given to certain patient groups
• Monitoring whether a previously negative result has turned positive

How do you prepare for the CMV IgG test?

You do not need to fast or wait for a particular time of day for the CMV IgG test. Telling your doctor how many weeks pregnant you are if you are pregnant, or letting them know if you are preparing for a transplant or receiving immunosuppressive treatment, helps ensure the result is evaluated correctly. If you have received blood products or immunoglobulin in recent months, mention this too, as antibodies transferred from outside can affect the result.

If you have had CMV tests before, it is important to keep the results; in particular, a change from negative to positive is one of the strongest signs of a new infection. The sample is taken from the arm; during pregnancy, sitting or lying down for the blood draw helps you stay comfortable and avoid dizziness. If you would like to avoid travel and crowded waiting rooms during pregnancy, your sample can also be taken by a nurse who comes to your home.

What does the CMV IgG result mean?

A positive result shows that you have been exposed to CMV in the past and that the virus is present in your body in a dormant state; in healthy people, it usually requires no treatment. A positive result before pregnancy rules out the possibility of being infected for the first time during pregnancy; however, reactivation or reinfection with a different strain can rarely occur. If IgM is also positive, your doctor may order an IgG avidity test to understand when the infection occurred. IgG detected in newborns and young infants is mostly antibodies passed from the mother through the placenta and does not on its own show that the baby is infected.

A negative result shows that you have not been exposed to CMV before and have no immunity against the virus. In that case, especially during pregnancy, simple hygiene measures are recommended, such as washing your hands after contact with young children's saliva and urine and not sharing cutlery or cups. The positivity threshold varies by laboratory and method, and interpretation can also differ depending on characteristics such as age, sex and pregnancy status; this laboratory's reference information is provided on this page. It is your doctor who will evaluate what the result means for your personal situation, together with your symptoms and other tests.