Mononucleosis diagnosis summary
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Lakshmi Gopalakrishnan, M.B.B.S. [2]
Overview
- If antibodies to the viral capsid antigen are not detected, the patient is susceptible to EBV infection.
Diagnosis Summary: Based on the Stage of Infection
Primary Infection
- Primary EBV infection is indicated if IgM antibody to the viral capsid antigen is present and antibody to EBV nuclear antigen (EBNA), is absent.
- A rising or high IgG antibody to the viral capsid antigen and negative antibody to EBV nuclear antigen after at least 4 weeks of illness is also strongly suggestive of primary infection.
- In addition, 80% of patients with active EBV infection produce antibody to early antigen.
Past Infection
- If antibodies to both the viral capsid antigen and EBV nuclear antigen are present, then past infection (from 4 to 6 months to years earlier) is indicated.
- Since 95% of adults have been infected with EBV, most adults will show antibodies to EBV from infection years earlier.
- High or elevated antibody levels may be present for years and are not diagnostic of recent infection.
Reactivation
- In the presence of antibodies to EBV nuclear antigen, an elevation of antibodies to early antigen suggests reactivation.
- However, when EBV antibody to the early antigen test is present, this result does not automatically indicate that a patient's current medical condition is caused by EBV.
- A number of healthy people with no symptoms have antibodies to the EBV early antigen for years after their initial EBV infection. Many times reactivation occurs subclinically.
Chronic EBV Infection
- Reliable laboratory evidence for continued active EBV infection is very seldom found in patients who have been ill for more than 4 months.
- When the illness lasts more than 6 months, it should be investigated to see if other causes of chronic illness or chronic fatigue syndrome (CFS) are present.
| Antibody (AB) | Time of appearance | Persistence | % Patients present |
| Viral capsid antigen-IgM (VCA-IgM) | At clinical presentation | 1-3 months | 100% |
| Viral capsid antigen-IgG (VCA-IgG) | At clinical presentation | Lifelong | 100% |
| Early antigen-IgG (EA IgG) | Peak 3-4 weeks after onset | 3-6 months | 70% |
| EBV nuclear antigen-IgG (EBNA IgG) | 6-12 weeks after onset | Lifelong | 100% |