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Mononucleosis spot test

The mononucleosis spot test looks for two antibodies in the blood that appear during or after an infection with the virus that causes mononucleosis or mono.

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

No special preparation is necessary.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

The mononucleosis spot test is done when symptoms of mononucleosis are present. Common symptoms include:

  • Fatigue
  • Fever
  • Large spleen (possibly)
  • Sore throat
  • Tender lymph nodes along the back of the neck

This test looks for antibodies called heterophile antibodies, which form in the body during the infection.

Normal Results

A negative test means there were no heterophile antibodies detected. Most of the time this means you do not have infectious mononucleosis.

Sometimes, the test may be negative because it was done too soon (within 1 to 2 weeks) after the illness started. Your health care provider may repeat the test to make sure you do not have mono.

A small number of people with mononucleosis may never have a positive test.

What Abnormal Results Mean

A positive test means heterophile antibodies are present. These are most often a sign of mononucleosis. Your health care provider will also consider other blood test results and your symptoms.

Antibodies reach their peak levels in 2 to 5 weeks, and may be present for up to 1 year.

In rare cases, the test is positive even though you do not have mono. This is called a false-positive result and it may occur in persons with:

  • Hepatitis
  • Leukemia or lymphoma
  • Rubella
  • Systemic lupus erythematosus (SLE)
  • Toxoplasmosis

Risks

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

Alternative Names

Monospot test; Heterophile antibody test; Heterophile agglutination test; Paul-Bunnell test; Forssman antibody test

References

Costello M, Sabatini, Yungbluth M. Viral infections. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 55.

Schooley RT. Epstein-Barr virus infection. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 385.

Weber R. Pharyngitis. In: Bope ET, Kellerman RD, eds. Conn's Current Therapy 2012. 1st ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 1.

Update Date: 5/12/2014

Updated by: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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