Monospot Test

A monospot test is used to diagnose infectious mononucleosis (often referred to as mono). The test detects certain antibodies that the body produces to fight the viruses that cause mono. Since it takes awhile for antibodies to develop, the first monospot test can be inaccurate and may need to be repeated one to two weeks after the symptoms first appear. If a person's symptoms and physical exam lead the doctor to suspect mono, he or she can also order other tests to confirm the diagnosis.

 

Monospot Test: An Overview

A monospot test is a blood test that is used to help diagnose mononucleosis, also known as "mono."
 

How Does a Monospot Test Work?

A monospot test works by detecting certain proteins called heterophile antibodies. The body makes these proteins to fight the Epstein-Barr virus (EBV) or cytomegalovirus (CMV) -- the two viruses that cause mono (see Mononucleosis Causes).
 

Can a Person With Mono Have a Negative Monospot Test?

Since it takes awhile for antibodies to develop after you're infected, it's possible for the first monospot test to be negative, even if you do have mono. The doctor may need to order or repeat the test one to two weeks after you develop the possible symptoms of mono. At that time, the monospot test comes back positive (meaning that a mono infection is present) in about 85 percent of people with mono.
 

Can a Person Without Mono Have a Positive Monospot Test?

It's possible for a person to have a positive monospot test and not have mononucleosis. A positive monospot test can also occur in people with:
 
  • Lymphoma
  • Systemic lupus erythematosus (lupus)
  • Certain gastrointestinal cancers.
     
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Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: Arthur Schoenstadt, MD