Monospot Test

A monospot test is a blood test that is used to help diagnose mononucleosis, also known as “mono. It is frequently ordered along with a CBC (complete blood count). The CBC is used to determine whether the number of white blood cells (WBCs) is elevated and whether a significant number of reactive lymphocytes are present.

The 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.

A strep test may also be ordered with the mono test to determine whether a person’s sore throat is due to strep throat, a streptococcal infection instead of or in addition to mononucleosis.

If the mono test is initially negative, the doctor still suspects mono, he may order a repeat test in a week or so to see if heterophile antibodies  have developed and/or order one or more EBV antibodies to help confirm or rule out the presence of a current EBV infection.

Additional tests that can help your doctor make a mononucleosis diagnosis include:

  • A complete blood count (CBC) to see if your blood platelet count is lower than normal and if your lymphocytes (lymph cells) are abnormal
  • A chemistry panel to see if your liver enzymes are abnormal.