Explanation

EBV IgM antibodies (VCA IgM): what is measured?

In a first infection with the Epstein-Barr virus (EBV), the immune system makes IgM antibodies against the coat of the virus (viral capsid antigen, VCA). VCA IgM is mainly present in the first weeks to months of the infection and then disappears. That is why it is a sign of a recent infection, as in active mononucleosis (glandular fever). The result is assessed together with VCA IgG and EBNA IgG.

What can it detect?

A recent first EBV infection (mononucleosis), together with VCA IgG and EBNA IgG

Result

What does the result mean?

Positive result

A positive VCA IgM fits a recent infection with the Epstein-Barr virus, especially if EBNA IgG is negative. In teenagers and young adults this often goes together with a sore throat, fever, swollen and painful glands and tiredness that can last 2 to 3 months. IgM can also be falsely positive, for example during an infection with another virus such as CMV. If EBNA IgG is already positive, it is probably not a new infection and the IgM result is harder to interpret. Rarely, the illness causes complications, such as an inflamed liver or a rupture of an enlarged spleen.

Negative result

A negative VCA IgM makes a recent infection with the Epstein-Barr virus unlikely. Symptoms such as a sore throat, fever or tiredness then probably have another cause. Very early in the illness, IgM may not quite be detectable yet.

After an abnormal result

With a result that fits a recent infection, the illness usually clears up on its own; the GP assesses the symptoms and looks out for rare complications. With an unclear pattern, the laboratory can do a confirmation test or the test is repeated after a few weeks. Mononucleosis is not notifiable.

Reliability

How reliable is the test?

According to the test guide of UMC Utrecht, VCA IgM serves to show a recent first infection, always together with VCA IgG and EBNA IgG. The combination usually gives a clear picture; a single positive IgM is less reliable, because cross-reactions with other viruses occur. According to UMC Utrecht, a rapid test for so-called heterophile antibodies is less sensitive and less specific than these EBV-specific tests.

What can affect the result?

Other viral infections, such as CMV, can give a false-positive IgM.
Very early in the illness, IgM can still be negative.
Test methods and cut-off values differ by laboratory.

Who it is for

Who is the test useful for?

Useful for

The result says the most with symptoms that fit mononucleosis, such as a sore throat, fever, swollen glands and marked tiredness, especially in teenagers and young adults. In people without symptoms or with long-lasting tiredness without a recent illness, a positive result says little: a recent infection is then unlikely and a false-positive IgM does occur.

How common is it?

Infection with the Epstein-Barr virus is very common in the Netherlands: half of the population over 5 years old has had the infection, and most adults had it before the age of twenty, usually without noticing. In teenagers and young adults the infection more often causes symptoms, such as a sore throat, fever, swollen glands and tiredness that can last 2 to 3 months.

RIVM, mononucleosis (glandular fever)

Drawbacks and risks

A false-positive IgM can wrongly attribute symptoms to mononucleosis, so that another cause is found later.

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