Explanation

EBV blot (confirmation test): what is measured?

The Epstein-Barr virus (EBV) causes mononucleosis (glandular fever) and then stays in the body for life. Separate antibody tests (VCA IgM, VCA IgG and EBNA IgG) each measure the response against one part of the virus. In an immunoblot, separate proteins of the virus are placed on a strip, so it becomes visible which proteins the antibodies in your blood react to. This makes it easier to assess whether it is a first infection or an infection from long ago: antibodies against the nuclear protein EBNA only develop months after the first infection. As a confirmation test, the blot mainly says something if the pattern of those separate tests is unclear or contradictory.

What can it detect?

Confirmation of a recent first infection with the Epstein-Barr virus (mononucleosis)
Confirmation of an infection from long ago, with an unclear pattern of results

Result

What does the result mean?

Positive result

Antibodies against one or more proteins of the Epstein-Barr virus were found. Which pattern of proteins lights up determines the meaning. If the antibodies react mainly to proteins of the virus coat and not to the nuclear protein EBNA, this fits a first infection in the last few months, as in mononucleosis. If there are also antibodies against EBNA, it is an infection from some time ago. Almost all adults have these antibodies; a positive result therefore says little on its own about the cause of symptoms.

Negative result

No antibodies against proteins of the Epstein-Barr virus were found. You have then probably never had the infection, which is uncommon in adults. Very early in a first infection the antibodies may still be absent; if there is a clear suspicion, the test is then repeated after a few weeks or the virus is looked for with a PCR.

After an abnormal result

The result is assessed together with VCA IgM, VCA IgG and EBNA IgG. If the pattern fits a recent first infection, the illness usually clears up on its own and the GP watches for rare complications such as an inflamed liver or an enlarged spleen. If the picture stays unclear, the test can be repeated after a few weeks or a PCR follows. Mononucleosis is not notifiable.

Reliability

How reliable is the test?

The blot is meant as confirmation when the standard EBV tests show an unclear pattern, for example a single positive VCA IgM without a fitting clinical picture. According to the test guide of UMC Utrecht, VCA IgM, VCA IgG and EBNA IgG are always assessed together; a rapid test for so-called heterophile antibodies is less sensitive and less specific than these EBV-specific tests. As a stand-alone first test the blot has little value, because almost everyone has antibodies. The result says nothing about the amount of virus in the body; that requires a PCR.

What can affect the result?

Almost all adults have antibodies against EBV; a positive result therefore does not automatically distinguish between a recent and an old infection.
Very early in a first infection, antibodies may still be absent.
With reduced immunity, the antibody pattern can be abnormal and hard to interpret.
The result says nothing about the amount of virus or about it becoming active again; that requires a PCR.

Who it is for

Who is the test useful for?

Useful for

Meant as confirmation with an unclear or contradictory pattern of the standard EBV tests, usually with symptoms that fit mononucleosis. In people without symptoms or with long-lasting tiredness without a recent illness, the result changes little: almost everyone has antibodies, and these then say nothing about the cause of the symptoms.

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 positive result occurs in almost everyone; still, long-lasting symptoms can wrongly be attributed to it, so that another cause is found later.

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