EPSTEIN BARR VIRUS AB VCA IGM
- EPSTEIN BARR VIRUS AB VCA IGM
- Start Date
- Expiration Date
- EBV VCA IgM, VCA-IgM
- CPT Codes
- Reference Test
- Transport Info
- Fasting Required?
- Patient Instructions
- Reference Range
An antibody index (AI) will be reported with the following interpretive information:
– Negative: Less than or equal to 0.8 AI
– Equivocal: 0.9-1.0 AI
– Positive: Equal to or greater than 1.1 AI
Multiplex Flow Immunoassay
Epstein-Barr Virus (EBV), a member of the herpesvirus group, is the etiologic agent of Infectious Mononucleosis (IM). EBV infections are difficult to diagnosis in the laboratory, in part because the virus does not grow in standard cell cultures. The majority of infections can be recognized, however, by testing the patient’s serum for heterophile antibodies, which usually appear in the first 3 weeks of illness and then decline rapidly within the next few weeks. The heterophile antibody, however, fails to develop in 10% of adults with IM, fails in a greater percentage of children with IM and is usually negative in infants with EBV infections. Although many of the cases of heterophile negative IM-like infections are due to cytomegalovirus (CMV), EBV cannot be ruled out without additional testing. Other antibody tests (IgG and IgM vs. Viral Capsid Antigen [VCA/IgG and VCA/IgM]; IgG vs. EB Nuclear Antigen [EBNA/IgG]; and IgG vs. Early D Antigen [EA-D]) are often useful in detecting heterophile negative cases of IM Note: These additional tests are recommended in heterophile-negative patients with clinical signs and symptoms of IM.
– IgG and IgM vs. Viral Capsid Antigen:
The presence of Viral Capsid Antigen IgM antibodies (VCA/IgM) indicates recent primary infection with EBV. It is detected in almost 100% of cases with high titers and is usually present in the serum before the onset of clinical symptoms. These antibody levels start to fall by the third week and disappear in 1-6 months. Note: VCA/IgM may sometimes be seen in other herpesvirus infections (especially CMV). Therefore, confirmation with IgG and EBNA assays are recommended. In addition sometimes serologic testing for VCA/IgM is requested after the antibody level has fallen below detectable limits, another indication for additional testing. Testing for VCA/IgM is a confirmatory test and should not be performed as a screening procedure in the general population. It should only be performed in patients suspected clinically of having IM. The predictive value of a positive or negative test depends greatly on the clinical likelihood of EBV associated disease. The presence of Viral Capsid IgG antibodies (VCA/IgG) indicates EBV infection sometime in the past and immunity. It also appears early in the illness and is detected in almost all cases. Its levels fall slightly during convalescence but are detectable for years after the illness. Because over 90% of normal adults have detectable VCA/IgG levels, it is not useful as a screen for IM in symptomatic adults. EBV is also associated with Burkitt’s Lymphoma and B-cell lymphomas in immunosuppressed or immunocompromised patients as well as in patients with poorly differentiated nasopharyngeal carcinoma. VCA/IgG antibody levels are positive in these patients.
– IgG vs. Epstein-Barr Nuclear Antigen:
Epstein-Barr Nuclear antibodies (EBNA) are the last antibodies to appear in IM. They are rarely present in the acute phase of the illness. EBNAs are detectable a few weeks after the onset of clinical symptoms, their levels rise during convalescence (3-12 months) and persist for many years. Absent EBNA and presence of VCA antibodies indicates acute infection.
– IgG vs. Early D Antigen:
Early antigen anti-D (EA-D) titers rise later in the course of IM than VCA antibodies but before the appearance of EBNA antibodies. They usually present 3-4 weeks after clinical onset of disease and disappear after clinical recovery. When present and combined with the presence of VCA/IgG they suggest recent EBV infection. However, antibodies vs. Early D antigen are seen in only 70% of patients with IM due to EBV. IgG vs. Early D Antigen is also seen in many patients with poorly differentiated nasopharyngeal carcinoma.
Acute primary EBV infection is indicated by one of the following serologic findings:
1. VCA/IgM found early during clinical symptoms and later disappears
2. Brief appearance of Early D Antigen followed by its disappearance
3. Early VCA/IgG without EBNA and later appearance of EBNA
The presence of IgM antibodies to VCA is normally detected in acute infectious mononucleosis (IM). However, it may not be detected in all acute IM patients. Although the heterophile antibody (latex slide) test is commonly used to diagnose acute IM, up to 20% of patients with primary Epstein-Barr Virus (EBV) infection do not develop heterophile antibodies. Testing for both heterophile antibody and anti-VCA IgM increases the likelihood of detecting acute primary infection.