When diagnosing Mononucleosis (Mono), should I order Epstein-Barr Virus (EBV) Immunoglobulin G (IgG) or Immunoglobulin M (IgM)?

From the Guidelines

To diagnose mono, you should order EBV IgM as it is the most indicative of a current infection. When looking to diagnose mono, it's essential to understand the role of Epstein-Barr Virus (EBV) antibodies in determining the infection status. According to the 2013 recommendations by the Infectious Diseases Society of America (IDSA) and the American Society for Microology (ASM) 1, EBV IgM antibodies are crucial for identifying current infection.

• EBV IgM antibodies appear early in the infection, typically becoming detectable 1-2 weeks after symptom onset and persisting for 1-3 months.
• EBV IgG antibodies, on the other hand, develop later and remain positive for life, indicating past infection and immunity. Key points to consider when ordering tests for mono include:
• The presence of VCA IgM (with or without VCA IgG) antibodies in the absence of antibodies to EBNA indicates recent primary infection with EBV 1.
• The presence of EBNA antibodies indicates infection more than 6 weeks from the time of the sample and therefore not likely implicating EBV as a cause 1. Given this information, ordering EBV IgM is the most direct approach to diagnosing a current mono infection, as it directly indicates an active or recent infection. While a complete EBV antibody panel can provide a more comprehensive assessment of infection status, if limited to a single test, EBV IgM is more diagnostically useful than IgG alone 1.

From the Research

Diagnosis of Mono

To diagnose Mono, also known as infectious mononucleosis, the following tests can be used:

• Heterophil antibody test (Monospot test)
• Serologic testing for antibodies to viral capsid antigens

EBV IgG and IgM Antibodies

When it comes to EBV IgG and IgM antibodies:

• IgM antibody to EBV viral capsid antigen is the most valuable serologic finding for diagnosing acute primary EBV infection 2
• IgM antibodies disappear within 8 to 10 weeks, whereas IgG antibodies remain at an almost constant level 3
• The presence of IgM antibody to EBV indicates a recent infection, while IgG antibody indicates a past infection 3

Ordering EBV IgG or IgM

If you are looking for Mono, you should order:

• EBV IgM to detect a recent infection 2, 3
• EBV IgG to detect a past infection 2, 3 Note that the diagnosis of infectious mononucleosis may be made when IgG-VCA, IgM-VCA, and anti-D antibodies are present and EBNA antibodies are absent 4