Tests

1st tests to order

CBC

Test
Result
Test

Lymphocytosis with greater than 50% lymphocytes seen in 70% cases.[34] Highest in second and third week.[53]

Atypical lymphocytosis greater than 10% seen in up to 90% cases, but is not specific for Epstein-Barr virus (EBV).[34]

Anemia and reticulocytosis can also identify patients with hemolytic anemia secondary to EBV infection.

Hematologic abnormalities can be absent in young children.

The sensitivity of this test is moderate.[40]

Result

lymphocytosis, atypical lymphocytosis

Epstein-Barr virus (EBV)-specific antibodies

Test
Result
Test

This test has a high sensitivity and specificity and is more sensitive than heterophile antibody test; the sensitivity of 6 commercial tests ranged from 95% to 99% and specificity from 86% to 100%.[37][39][40] It is often positive in young children with asymptomatic disease.

The specific antigens are important for distinguishing between acute and past infection.

Viral capsid antigen-IgM (VCA-IgM) in most patients is detectable with symptom onset; peaks at 2 to 3 weeks; becomes unmeasurable by 4 months.

VCA-IgG peaks at 2 to 3 months; persists for life.

Antibodies to early antigens (EA) rise in acute stage; become undetectable by 3 to 4 months; may reappear with reactivation of EBV infection. EA antibodies are also detectable in some clinically healthy persons.

Nuclear antigen (EBNA) antibodies rise in resolution phase, and remain detectable for life.[41] These antibodies develop after 6 to 8 weeks and can be used to identify past infection, or as evidence to rule out acute EBV infection.[42]

Detection of EBV antibodies, VCA-IgG, VCA-IgM, and EBNA is possible in cerebrospinal fluid of patients with EBV encephalitis.[54]

Result

positive for EBV-specific antibodies: VCA-IgM, VCA-IgG, EA, EBV EBNA

LFTs

Test
Result
Test

Transaminase elevations are usually transient and mild (2-3 times the upper limit of normal), but in some patients much higher transaminase elevations (5-10 times the upper limit of normal) are observed.[51]

Result

elevated

Investigations to avoid

serum Monospot for EBV infection

Recommendations
Rationale
Recommendations

Do not order a serum Monospot test.[38]

Rationale

The Centers for Disease Control and Prevention recommend that the Monospot test is not used. The antibodies detected by Monospot can be caused by conditions other than infectious mononucleosis and do not confirm the presence of EBV infection.[38]

ultrasonography of abdomen

Recommendations
Rationale
Recommendations

Do not routinely order abdominal ultrasound in athletes with infectious mononucleosis to detect splenomegaly.[45][46]

Rationale

Comparing an individual’s splenic size to population norms is not a valid method to assess splenic enlargement.[45][47]

Tests to consider

real-time polymerase chain reaction (PCR)

Test
Result
Test

Real-time PCR is when the amplified DNA is detected as the reaction progresses in real time. Test has 95% sensitivity and 97% specificity for primary EBV infection.[55]A meta-analysis found that pooled sensitivity for detecting EBV DNA by PCR was 77% and pooled specificity was 98%.[56]

Is expensive and not commonly used in clinical practice.

Test can be useful for diagnosis of serologically indeterminate EBV infections.[43]

EBV nucleic acid amplification test is useful for detecting EBV in the cerebrospinal fluid of patients with EBV encephalitis.[54]

Emerging data shows that PCR has a higher diagnostic value than VCA-IgG in children ages <6 years, especially those ages <3 years.[57]

Result

EBV DNA detection

CT of abdomen

Test
Result
Test

Performed on a hemodynamically stable patient when splenic rupture is suspected.

Result

splenic rupture

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