Blood draw
CMV (IgG and IgM)
CMV-IgM and IgG; recent or past infection.
€ 45,00
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Infections · Blood
CMV IgM
Antibodies that may point to a recent CMV infection; can only be properly interpreted together with IgG.
At a glance
- Measured in blood
- In 1 test panel
- No special preparation
Explanation
CMV IgM: what is measured?
With an infection with cytomegalovirus (CMV), the immune system first makes IgM antibodies and shortly afterwards IgG. According to the LCI guideline (RIVM), IgM is detectable for 4 to 6 months after the infection and is therefore used as a sign of a recent infection. Sometimes IgM also appears when an old infection becomes active again. The result is always assessed together with IgG.
What can it detect?
- Possible recent CMV infection (together with IgG)
- Reason for further testing with symptoms or during pregnancy
Result
What does the result mean?
Positive result
A positive IgM may fit a recent CMV infection, but does not prove it. IgM can remain detectable for months, can come back when an old infection becomes active again, and can be a false positive, for example during another viral infection such as glandular fever (Pfeiffer's disease). In healthy adults, a CMV infection usually causes no symptoms, or fever, sore throat, swollen glands, tiredness and slightly abnormal liver values. For the pregnant woman herself, a CMV infection is no more dangerous than for others; the risk concerns the unborn baby, especially with a first infection early in pregnancy.
Negative result
A negative IgM makes a recent CMV infection unlikely. Together with a positive IgG, this fits an infection some time ago; together with a negative IgG, it usually means that you have not had CMV yet. According to the LCI guideline (RIVM), a negative IgM in a pregnant woman does not fully rule out an infection of the unborn baby, for example with reactivation or reinfection.
After an abnormal result
With a positive IgM, the GP or midwife usually has blood taken again after a few weeks or has the IgG avidity measured. If a first infection during pregnancy is suspected, referral to the gynecologist follows for further testing, such as an ultrasound and possibly amniotic fluid testing. CMV is not notifiable.
Reliability
How reliable is the test?
According to the LCI guideline (RIVM) on CMV infection, the IgM test is sensitive in the first phase of an infection, but the specificity depends on the test used, so false-positive results occur. A recent infection is therefore established with a combination of IgM, IgG, an IgG avidity test and, if possible, comparison with a previously taken blood sample. If an infection of the unborn baby is suspected, IgM in the mother is not sensitive enough to rule it out.
What can affect the result?
- IgM can remain detectable for 4 to 6 months after the infection and can also appear with reactivation.
- Other viral infections, such as with the Epstein-Barr virus, can give a false-positive IgM.
- Tests differ between laboratories; a weakly positive result is hard to interpret.
Who it is for
Who is the test useful for?
Useful for
Useful with symptoms that may point to a recent CMV infection, such as fever, tiredness and swollen glands, especially if testing for glandular fever (Pfeiffer's disease) is negative, in a pregnant woman with such symptoms or with abnormalities in the baby on the ultrasound, and in people with a reduced immune system. Not useful as screening before or during pregnancy without symptoms: according to the LCI guideline (RIVM), the result is then hard to interpret and there is no treatment that prevents transmission.
How common is it?
According to the LCI guideline (RIVM), the chance of a first CMV infection during a pregnancy is less than 1 percent. About 1 in 200 newborns in the Netherlands has a congenital CMV infection; about half of these result from a first infection in the mother, the other half from reactivation or reinfection.
LCI guideline (RIVM) on CMV infection
Drawbacks and risks
- A false-positive or long-lasting IgM can cause a lot of worry and extra testing, especially during a pregnancy.
- A negative IgM can wrongly reassure you: even after a previous CMV infection, an unborn baby can become infected.
Get tested
CMV IgM: test panels
CMV IgM is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and resultsMore explanations
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