Which lab studies are specific for Epstein-Barr virus (EBV) infectious mononucleosis (mono)?

Updated: Sep 20, 2018
  • Author: Burke A Cunha, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

Specific tests are as follows:

  • Heterophile antibody tests

    • Patients with infectious mononucleosis should first be tested with a heterophile antibody test. The most commonly used is the latex agglutination assay using horse RBCs, and it is marketed as the Monospot test. Enzyme-linked immunosorbent assay (ELISA) rapid diagnostic tests are also available, which are based on the detection of heterophile antibodies. Physicians should remember that heterophile antibody responses require 1-2 weeks to become positive. In a group of patients with EBV mononucleosis, the number of patients becoming positive increases to a maximum 6 weeks after the onset of the illness.

    • If results are initially negative, a Monospot test should be ordered weekly for 6 weeks in patients with suspected EBV infectious mononucleosis. If the Monospot test remains persistently negative after 6 weeks of weekly serial testing, then a specific EBV serological test should be ordered. Before patients with an infectious mononucleosis–like syndrome are labeled as having heterophile-negative infectious mononucleosis, specific EBV serological tests should be obtained, and the results should be negative (see below).

    • Major antibodies - Heterophile (Paul-Bunnell), EBV antigens, cold agglutinins (anti-1), smooth muscle antibodies (SMA)

    • Minor antibodies - Rheumatoid factor (RF), antinuclear antibodies (ANA), antimitochondrial antibodies, antireticulin antibodies, antimicrosomal antibodies, anti–intermediate filaments (IMF), lymphocytotoxin, Wasserman reagin

    • The Monospot test has high sensitivity and specificity, eg, 85% and nearly 100%, respectively. Rarely, Monospot test results may be falsely positive, particularly in patients with CMV or rubella but also in patients with SLE and rheumatoid arthritis. Potential false-positive reactions may occur in those with HIV infection or herpes simplex virus (HSV). If a false-positive Monospot test result is suspected, then specific testing using an EBV-based antibodies serological test is indicated. A false-negative Monospot test result may occur if testing is performed too early in the course of the illness or in very young children (< 2 y) and occasionally in elderly patients.

  • Specific EBV antibody tests

    • Specific EBV antibody testing is more time-consuming and expensive than the Monospot test. EBV serological tests should be obtained in patients with a mononucleosislike illness and a negative finding on the Monospot test. As with the heterophile test, the EBV antibody response may be falsely negative early in the course of the infection. False negativity may also occur in young children (< 2 y).

    • The antibody response to specific EBV serological testing consists of measuring the antibody response to surface and core EBV viral proteins. For clinical purposes, the most useful EBV-specific antibodies are the VCAs and the EBNA. Both VCA and EBNA antibodies are usually reported as IgM or IgG antibodies. Acute infection is diagnosed in patients who have an increased EBV IgM VCA titer. Later in the course of infection, the increase in IgM VCA antibodies may be accompanied by an increase in IgG VCA antibodies and an increase in IgG EBNA antibodies. Many laboratories report EBNA titers only, which usually measure the IgG EBNA.

    • Increased IgG VCA and/or increased IgG EBNA titers indicate past exposure to EBV, which may have been subclinical or clinical. Increased IgG VCA titers are not synonymous with chronic infectious mononucleosis, and these titers are not diagnostic of CFS. Following acute infection, the increase in IgM titers peaks after 4-8 weeks and usually remain positive for as long as 1 year. The Monospot heterophile antibodies follow the same time course as the IgM VCA titers.

    • Rarely, cross-reactivity occurs between VCA antibodies to EBV and those to CMV or toxoplasmosis. False-positive cross-reactivity to specific EBV antibodies is extremely rare. Such patients have high elevations of IgM CMV or toxoplasmosis titers, which helps to differentiate between the primary infectious agent and the serological cross-reactivity resulting in a false-positive test result.

    • Patients with heterophile-negative infectious mononucleosis, eg, those with persistently negative Monospot test results for 6 weeks and those with a negative EBV-specific test result, should be tested serologically for the infectious agents that cause heterophile-negative infectious mononucleosis (eg, HIV, HHV-6, toxoplasmosis, CMV, rubella, anicteric viral hepatitis).

Table 2. EBV Serologic Responses in EBV-Associated Diseases (Open Table in a new window)

EBV Diseases

EBV Antibody Responses

Anti-VCA

Anti-EA

IgM

Monospot/

Heterophile

IgM

IgG

Diffuse EA

Restricted EA

Anti-EBNA

Acute EBV mononucleosis

+

+

+

+

-

-

Past EBV infection

-

-

+

-

-

+

Chronic active EBV infection

-

-

+++

+

+

+

Burkitt lymphoma

-

-

+++

+/-

+

+

Nasopharyngeal carcinoma

-

-

+++

+

+/-

+


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