Monospot test

Synonym

Tubes

Additional information

Info

This test is ordered to evaluate for infectious mononucleosis (Epstein-Barr Virus infection)
The monospot test is a rapid slide agglutination test to detect the presence of heterophile antibodies in the blood
Heterophile antibodies are IgM immunoglobulins synthesized by B-cells during Epstein-Barr virus (EBV) infection and is the laboratory hallmark of infectious mononucleosis
The basis of monospot test is the agglutination reaction of horse red blood cells on exposure to heterophile antibodies (qualitative), which can be titered (quantitative analysis)

Clinical

As a screening test to detect infectious mononucleosis in persons presenting with symptoms of mononucleosis-like syndrome
In pregnant women presenting with flu-like symptoms
Evaluation of recent EBV infection
To distinguish EBV infection from other causes of mononucleosis-like syndrome or glandular fever such as:

Primary infection by EBV in young children is often asymptomatic or mild. However, in adolescents and young adults it manifests as infectious mononucleosis, a self-limited clinical syndrome
EBV is transmitted primarily by saliva through close mucocutaneous contact (hence also known as kissing disease) and has a very long incubation period (4–8 weeks)
Infectious mononucleosis may be clinically characterized as:

Fever (97% cases, persists for 7-10 days)
Sore throat or exudative pharyngitis (>97%, disappears within 14 days after onset)
Lymphadenopathy (>97% cases, most common affected is posterior cervical, axillary, and inguinal)
Chills
Malaise
Fatigue
Myalgias
Splenomegaly (75%, regresses by 21–28 days)
Palatal petechiae (50%)
Periorbital edema (33%)
Hepatomegaly (20%, regresses by 21–28 days)
Maculopapular rash (10%)

It appears about 1 week after the onset of the disease (detectable in 50% cases), peaks at 2-5 weeks (detectable in 60-90% cases), and declines to a low titer ( 1:40) for 2-3 months after the onset of symptoms to 1 year (detectable in 75% cases), or up to 2 years (detectable in 20% cases)
Only 10-30% of children <2 years and 50-75% of children aged 2-4 years develop heterophile antibodies with primary EBV infection
Heterophile antibodies are not directed against EBV and react with cells (hemagglutination) of other species such as horse RBCs, bovine RBCs, or sheep red cells
These antibodies are not specific to infectious mononucleosis and are formed in serum sickness, drug reactions, and as naturally occurring antibodies to Forssman antigen

A repeat monospot test in 7-14 days is recommended if the initial test results are negative in the presence of a strong clinical suspicion of EBV infection {Also consider EBV antibody testing [anti-VCA IgM, anti-VCA IgG, anti-EA (D), EBNA IgG]}
The titer level does not typically correlate with the severity of the disease

Additional information

The three classic criteria for laboratory confirmation of acute infectious mononucleosis due to EBV include:

Nl Result

High Result

A positive monospot test is associated with infectious mononucleosis (90-95%)

Conditions associated with false positive monospot test results include:

Low Result

Conditions associated with false negative monospot test results include:

Children <2 years of age have up to 90% false positive rates
Children 2-4 years of age have 25-50% false positive rates
EBV associated with lymphoproliferative processes
EBV in immunosuppressed persons
Reactivated EBV infection
Early testing (<1 week) into illness often results in false negative result (need to retest in 1-2 weeks)
Not all patients develop heterophile antibodies (even at the peak at 2-5 weeks into the illness, up to 40% of patients still have a negative monospot test)

References

ARUP's Laboratories®. Infectious Mononucleosis Slide Test by LA. [Homepage on the Internet]©2007. Last accessed on February 7, 2007. Available at URL: http://www.aruplab.com/guides/ug/tests/0050385.jsp
Bell AT et al. Clinical inquiries. What test is the best for diagnosing infectious mononucleosis? J Fam Pract. 2006 Sep;55(9):799-802.
eMedicine from WebMD®. Mononucleosis and Epstein-Barr Virus Infection. [Homepage on the Internet] ©1996-2007. Last updated on May 23, 2006. Last accessed on February 7, 2007. Available at URL: http://www.emedicine.com/PED/topic705.htm
LabTestsOnline®. Monospot Test. [Homepage on the Internet]©2001-2007. Last reviewed on May 27, 2004. Last accessed on February 7, 2007. Available at URL: http://www.labtestsonline.org.uk/understanding/analytes/mono/sample.html
Papesch M et al. Epstein-Barr virus infectious mononucleosis. Clin Otolaryngol Allied Sci. 2001 Feb;26(1):3-8.
Ventura KC et al. Hematologic differences in heterophile-positive and heterophile-negative infectious mononucleosis. Am J Hematol. 2004 Aug;76(4):315-8.
Vidrih JA et al.Positive Epstein-Barr virus heterophile antibody tests in patients with primary human immunodeficiency virus infection. Am J Med. 2001 Aug 15;111(3):192-4.