The Test Sample
What is being tested?
Epstein-Barr virus (EBV) antibodies are a group of tests that are requested to help diagnose a current, recent, or past EBV infection. EBV is a member of the herpes virus family. Passed through the saliva, the virus causes an infection that is very common. As many as 95% of people in the United Kingdom will have been infected by EBV by the time they are 40 years old. After exposure to the virus, there is an incubation period of several weeks. EBV then causes an infection followed by resolution and then dormancy. EBV remains in the person’s body for the rest of their life, reactivating intermittently, but causing few problems unless the person’s immune system is significantly compromised.
Most people are infected by EBV in childhood and experience few or no symptoms, even during the infection. However, when the initial infection is delayed until adolescence, EBV causes glandular fever in about 35 – 50% of those infected. Glandular fever is a condition that is associated with tiredness, fever, sore throat, swollen lymph nodes, an enlarged spleen, and, sometimes, an enlarged liver. Those who have glandular fever usually have symptoms for a month or two before the infection gets better. A few people can have symptoms that last many months, but this is uncommon.
Patients with glandular fever are diagnosed by their symptoms and the findings of a full blood count (FBC) and a Monospot test (which tests for a heterophile antibody). A certain percentage of those who have glandular fever will have a negative monospot test; this is especially true with children. EBV antibodies can be used to find out whether or not the symptoms these patients are experiencing are due to a current infection with the EBV virus.
It can be important to distinguish EBV from other illnesses. For instance, the enlarged spleen of those with an EBV infection is vulnerable to rupture. Patients who have glandular fever should not be involved in contact sports for several weeks to months after infection, as a ruptured spleen can be a medical emergency. Also, pregnant women with symptoms of a viral illness need to be able to distinguish a primary EBV infection, which has not been shown to affect the baby, from a cytomegalovirus (CMV), herpes simplex virus, or toxoplasmosis infection, as these illnesses can cause complications during the pregnancy and may damage the growing baby. It can also be important to rule out EBV and to look for other causes for the symptoms. Patients with streptococcal sore throat, for instance, need to be identified and treated with antibiotics. A patient may have a streptococcal sore throat instead of EBV infection, or they may have both conditions at the same time.
There are several EBV antibodies. They are proteins produced by the body in an immune response to several different Epstein-Barr virus antigens. They include IgM and IgG antibodies to the viral capsid antigen (VCA), IgG antibodies to the D early antigen (EA-D), and antibodies to the nuclear antigen (EBNA). During a primary EBV infection, each of these EBV antibodies appears independently on its own time schedule. The VCA-IgM antibody appears first and then tends to disappear after about 4 to 6 weeks. The VCA-IgG antibody emerges, is at its maximum at 2 to 4 weeks, then drops slightly, stabilizes, and is present for life. The EA-D antibody appears during the acute infection phase and then tends to disappear within 3 to 6 months, but about 20% of those infected will continue to have detectible quantities of the EA-D antibody for several years after the EBV infection has resolved. The EBNA antibody does not usually appear until the acute infection has disappeared. It usually develops about 2 to 4 months after the initial infection and is then present for life, although it can fall to undetectable levels in elderly persons. Using a combination of these EBV antibody tests, a doctor is able to detect an EBV infection and to determine whether it is a current, recent, or past infection.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.