The mononuclear spot test or monospot test, a form of the heterophile antibody test, is a rapid test for

infectious mononucleosis Infectious mononucleosis (IM, mono), also known as glandular fever, is an infection usually caused by the Epstein–Barr virus (EBV). Most people are infected by the virus as children, when the disease produces few or no symptoms. In young adult ...

due to Epstein–Barr virus (EBV). It is an improvement on the Paul–Bunnell test. The test is

specific Specific may refer to: * Specificity (disambiguation) * Specific, a cure or therapy for a specific illness Law * Specific deterrence, focussed on an individual * Specific finding, intermediate verdict used by a jury in determining the fina ...

for

heterophile Heterophile antibodies are antibodies induced by external antigens ( heterophile antigens). Some cross-react with self-antigens. For example, in rheumatic fever, antibodies against group A streptococcal cell walls can also react with (and thus ...

antibodies produced by the human

immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...

in response to EBV infection. Commercially available test kits are 70–92% sensitive and 96–100%

, with a lower sensitivity in the first two weeks after clinical symptoms begin. The United States Center for Disease Control deems the monospot test not to be very useful.

Medical uses

It is indicated as a confirmatory test when a physician suspects EBV, typically in the presence of clinical features such as fever, malaise, pharyngitis, tender lymphadenopathy (especially posterior cervical; often called "tender glands") and

splenomegaly Splenomegaly is an enlargement of the spleen. The spleen usually lies in the left upper quadrant (LUQ) of the human abdomen. Splenomegaly is one of the four cardinal signs of ''hypersplenism'' which include: some reduction in number of circulating ...

.Davidson's Principles & Practices of Medicine 20th ed In the case of delayed or absent

seroconversion In immunology, seroconversion is the development of specific antibodies in the blood serum as a result of infection or immunization, including vaccination. During infection or immunization, antigens enter the blood, and the adaptive immune system ...

, an immunofluorescence test could be used if the diagnosis is in doubt. It has the following characteristics: VCAs (Viral Capsid Antigen) of the IgM class, antibodies to EBV early antigen (anti-EA), absent antibodies to EBV nuclear antigen (anti-EBNA)

Usefulness

One source states that the specificity of the test is high, virtually 100%,Infectious Mononucleosis Workup
from

Medscape Medscape is a website providing access to medical information for clinicians; the organization also provides continuing education for physicians and health professionals. It references medical journal articles, Continuing Medical Education (CM ...

. Author: Burke A Cunha, MD; Chief Editor: Michael Stuart Bronze, MD. Updated: Sep 21, 2011 Another source states that a number of other conditions can cause

false positive A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test result ...

s. Rarely, however, a false positive heterophile antibody test may result from

systemic lupus erythematosus Lupus, technically known as systemic lupus erythematosus (SLE), is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary among people and may be mild to severe. Comm ...

toxoplasmosis Toxoplasmosis is a parasitic disease caused by ''Toxoplasma gondii'', an apicomplexan. Infections with toxoplasmosis are associated with a variety of neuropsychiatric and behavioral conditions. Occasionally, people may have a few weeks or months ...

rubella Rubella, also known as German measles or three-day measles, is an infection caused by the rubella virus. This disease is often mild, with half of people not realizing that they are infected. A rash may start around two weeks after exposure and ...

lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlar ...

and

leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ' ...

. However, the sensitivity is only moderate, so a negative test does not exclude EBV. This lack of sensitivity is especially the case in young children, many of whom will not produce detectable amounts of the heterophile antibody and will thus have a false negative test result.

Timing

It will generally not be positive during the 4–6 week incubation period before the onset of symptoms. The highest amount of heterophile antibodies occurs 2 to 5 weeks after the onset of symptoms. Review Date 3/13/2016 If positive, it will remain so for at least six weeks. An elevated heterophile antibody level may persist up to 1 year.

Process

The test is usually performed using commercially available test kits which detect the reaction of heterophile antibodies in a person's blood sample with horse or cow red blood cell antigens. These test kits work on the principles of

latex agglutination A latex fixation test, also called a latex agglutination assay or test (LA assay or test), is an assay used clinically in the identification and typing of many important microorganisms. These tests use the patient's antigen-antibody immune respon ...

immunochromatography Affinity chromatography is a method of separating a biomolecule from a mixture, based on a highly specific macromolecular binding interaction between the biomolecule and another substance. The specific type of binding interaction depends on the ...

. Using this method, the test can be performed by individuals without specialized training, and the results may be available in as little as five minutes. Manual versions of the test rely on the agglutination of horse erythrocytes by heterophile antibodies in patient serum. Heterophile means it reacts with proteins across species lines. Heterophile also can mean that it is an antibody that reacts with antigens other than the antigen that stimulated it (an antibody that crossreacts). A 20% suspension of horse red cells is used in an isotonic 3–8% sodium citrate formulation. One drop of the patient's serum to be tested is mixed on an opal glass slide with one drop of a particulate suspension of guinea-pig kidney stroma, and a suspension of ox red cell stroma; sera and suspensions are mixed with a wooden applicator 10 times. Ten microliters of the horse red cell suspension are then added and mixed with each drop of adsorbed serum. The mixture is left undisturbed for one minute (not rocked or shaken). Examine for the presence or absence of

red cell agglutination In hematology, red cell agglutination or autoagglutination is a phenomenon in which red blood cells clump together, forming aggregates. It is caused by the surface of the red cells being coated with antibodies. This often occurs in cold agglutini ...

. If stronger with the sera adsorbed with guinea-pig kidney, the test is positive. If stronger with the sera adsorbed with ox red cell stroma, the test is negative. If agglutination is absent in both mixtures, the test is negative. A known 'positive' and 'negative' control serum is tested with each batch of test sera.

References

{{Clinical microbiology techniques Virology Infectious disease blood tests Epstein–Barr virus Immunologic tests