What is a mononucleosis spot test?
A mononucleosis spot (or Monospot) test is a blood test used to determine whether you have contracted the Epstein-Barr virus, the virus that causes infectious mononucleosis. Your doctor may order this test if you have symptoms of mononucleosis.
Mononucleosis is a viral disease that affects certain blood cells and creates flu-like symptoms.
What is mononucleosis?
Mononucleosis is a viral infection caused by the Epstein-Barr virus (EBV), which is a type of herpes virus and one of the most common human viruses. Also called “mono” and “the kissing disease,” the illness isn’t considered serious or life-threatening.
This disease typically affects teenagers and young adults in their 20s. The symptoms of infectious mononucleosis can make it difficult to continue with normal daily activities. Symptoms may last from several weeks to a couple of months. In rare cases, it can last several months.
Symptoms of mononucleosis include:
- sore throat
- swollen glands in neck and armpits
- severe fatigue
- body aches
- loss of appetite
- swollen spleen, liver, or both (uncommon)
If you have these symptoms for a week or longer, you may have mono. Your doctor may perform the mononucleosis spot test to confirm (or rule out) the diagnosis.
How does the test detect the virus?
When a virus infects the body, the immune system goes to work to fight it off. This is your body’s protective reaction. It includes the release of certain antibodies, or “fighter cells,” charged with going after the viral cells.
The mononucleosis test looks for the presence of two antibodies that typically form when certain infections — like those caused by the Epstein-Barr virus — are present in the body.
On rare occasions, the test may show antibodies even though you don’t have the infection. This may occur especially if you have:
- systemic lupus erythematosus
- other infectious diseases and some cancers
If the test comes back negative, it may mean you don’t have the infection or that the test was performed too early or too late to detect the antibodies. Your doctor might recommend a second test in a couple of weeks or may try other tests to confirm the diagnosis.
The Centers for Disease Control and Prevention (CDC)Trusted Source doesn’t recommend the Monospot test for general use because, while it may indicate whether you have infectious mononucleosis, it doesn’t confirm the presence of the Epstein-Barr virus.
What happens during a Monospot test?
This blood test is most often done once symptoms have developed, which is typically 4 to 6 weeks after exposure (this delay is referred to as the incubation period). The test helps to confirm a diagnosis of the illness.
Like most blood tests, it’s performed by a healthcare provider who draws a blood sample from a vein, usually on the inside of the elbow or the back of the hand. Sometimes a simple finger-prick test may be used instead.
Your healthcare provider will wrap an elastic band around your upper arm to make the vein fill with blood. They’ll then gently insert a small needle into the vein, allowing the blood to flow into an attached tube.
When the tube contains enough blood, your doctor will withdraw the needle and cover the small puncture wound with a bandage.
For a finger-prick test, your healthcare provider will make a small prick in the tip of your ring finger, then squeeze to collect enough blood in a small tube to perform the test. A bandage is placed over the small wound afterward.
Lab technicians place the blood sample on a microscope slide, mix it with other substances, and then watch to see if the blood begins to clump. If it does, the test is considered a positive confirmation of mononucleosis.