What is being tested?Epstein-Barr virus (EBV)
antibodies are a group of tests that are ordered 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. According to the National Center for Infectious Diseases (NCID), as many as 95% of people in the United States 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 acute infection, followed by resolution and dormancy. Latent EBV remains in the patient’s body for the rest of his life, reactivating intermittently, but causing few problems unless the patient’s immune system is significantly compromised.
Most people are infected by EBV in childhood and experience few or no symptoms, even in the acute phase of the infection. However, when the initial infection is delayed until adolescence, EBV causes infectious mononucleosis (Mono) in about 35 – 50% of those infected. Mono is a condition that is associated with fatigue, fever, sore throat, swollen lymph nodes, an enlarged spleen, and, sometimes, an enlarged liver. Those who have it are usually symptomatic for a month or two before the initial infection resolves.
Patients with Mono are diagnosed by their symptoms and the findings of a complete blood count (CBC) and a Mono test (which tests for a heterophile antibody). A certain percentage of those who have mono will have a negative mono test – this is especially true with children. EBV antibodies can be used to determine 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 a Mono infection is vulnerable to rupture. Patients who have Mono should not be involved in contact sports for several weeks to months after infection, as a ruptured spleen can cause 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 damage the fetus. It can also be important to rule out EBV and to look for other causes for the symptoms. Patients with strep throat (a Group A streptococcus infection), for instance, need to be identified and treated with antibiotics. A patient may have strep throat instead of Mono, or they may have both conditions at the same time.
There are several EBV antibodies. They are proteins created by the body in an immune response to different antigens (protein parts) of the Epstein-Barr virus. 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 resolved. It usually develops about 2 to 4 months after the initial infection and then is present for life. 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.
