Everything You Need To Know About the Mono (Mononucleosis) Blood Test

Mononucleosis (mono) is a common and generally mild viral disease, usually caused by the Epstein-Barr virus.

Over 90% of adults have been infected at some point and will display antibodies to the virus upon testing.

Many people infected with mono never have symptoms, and those who do experience generalized symptoms fatigue, fever, sore throat, and tender lymph nodes.

Because the symptoms of mono are similar to other viral illnesses, a couple of laboratory tests have been developed to determine the correct diagnosis.

These tests are the monospot test and the EBV test. 

Read on to discover what these lab tests are, how they are performed, how to prepare for them, and where you can get them done.

Lastly, this article goes over what your test results mean.

Mononucleosis Blood Test

Any age group is susceptible to infectious mononucleosis, but it is most commonly seen in adolescents and young adults, especially college students.

The symptoms of mono are very similar to those of other illnesses, which creates a dilemma when trying to correctly diagnose a patient.

For this reason, specific lab tests were developed to correctly diagnose mono. 

What is it?

The Epstein-Barr virus (EBV) is the most common cause of a mononucleosis infection.

This virus is in the herpes virus family and is passed from person to person through bodily fluids, especially saliva.

If you are exposed to the virus, you may never have an active infection.

If it does cause an infection, symptoms usually appear 4-6 weeks after the exposure and typically last 1-2 months.

When your body is fighting a mono infection, your immune system makes antibodies to help fight the EBV; this is what these tests look for.

Tests that are done may include: 

• Monospot test: This shows if you have specific antibodies in your blood. These antibodies are present during and after a mono infection. This is a rapid test; results are ready in about five minutes. Several factors can cause this test to be a false negative so the EBV antibody test is usually also ordered.
• EBV antibody test: Different antibodies are present depending on whether this is a current infection, or if you had one in the past. The EBV antibody test looks for these antibodies. If certain antibodies are present in your blood, it means you have a current mono infection and if you have other antibodies, it means you were infected in the past.
• Complete blood count (CBC): This test checks for high levels of white blood cells, which can indicate an infection.
• Throat culture: Strep throat and mono have similar symptoms; a throat culture will rule out strep.

Why is it done?

Your healthcare provider may order the mono tests if they think you have infectious mononucleosis. 

Symptoms of mono include:

• Fatigue or exhaustion
• Swollen lymph glands
• Sore throat
• Fever
• Enlarged spleen

When to get a test

A typical viral infection (e.g. the common cold) lasts about two weeks.

If you are still experiencing symptoms after two weeks, it would be a good idea to see your doctor.

They may prescribe for you to take a test. 

If taken too early, the lab test may give a false negative, so wait and take it after you’ve been sick for at least two weeks.

Risks

Any time you have blood drawn with a needle there are some risks, but they are minimal.

The risks include:

• Bleeding
• Bruising
• Feeling lightheaded
• Slight sting or pinch when the needle is inserted
• Soreness around site after the test
• Infection 

How Is a Mononucleosis Blood Test Done?

There are two ways the blood tests can be done: a finger stick or a blood draw from a vein.

A blood test from a finger stick

This is a simple and quick way to draw blood. The tip of your finger is cleaned with an alcohol pad.

The medical professional then does a quick pinprick on the tip of your middle or ring finger, and a drop of blood is collected in a tube for testing.

Your finger is cleaned with gauze, and they may give you a bandage. 

A blood test from a vein

Sometimes the blood is taken from a vein.

For this procedure, you sit in a chair and the medical professional places an elastic tourniquet around your upper arm.

Then, they use an alcohol swab to clean the skin over the vein that they are going to use.

You may be asked to make a fist or squeeze a ball to help the vein bulge. 

A tiny needle is inserted into your vein and the blood is suctioned into a couple of vials for testing. 

How To Prepare

Be sure your healthcare provider knows all medications you take including herbs, vitamins, over-the-counter medications, and any illegal drugs you may use.

These can affect lab results, so it’s important to let your doctor know ahead of time.

Before

Drink plenty of water before your lab test so your veins are easier to see in case you need blood drawn from your vein. (No one likes to get poked twice!)

There typically is nothing else you need to do to prepare for your test unless your doctor instructs you otherwise. 

During

During the test, you will be told if it will be a fingerstick or a vein draw.

The technician will go over the reason for the test as well as the benefits, side effects, and risks, and get your permission to perform the lab test.

If you are queasy around needles, let them know so they can make you more comfortable.

You will feel tightness from the tourniquet and may feel a little pinch when the needle penetrates your skin you, but that should be the only discomfort.

After

After your test is over, you will be asked to wait in the exam room or a waiting room until the results are ready.

The monospot test results are typically ready within ten minutes. 

Where Can I Get Tested?

After being ordered by a medical professional, the monospot test can be done at your doctor’s office, clinic, urgent care center, or emergency room.

Can I take the test home?

There are several self-test kits available for purchase online.

• Self-test kits allow you to collect a drop of your blood from a finger prick and run the test using the kit. Results are ready within 3-5 minutes.
• Self-collection kits have you collect your blood sample and mail it to the laboratory for testing. You will be notified of the results generally within a few days. 

Cost

The cost of your test will depend on a few factors, such as:

• If you have health insurance
• Where you get the test done
• Any additional testing that is needed

In general, a mono test on its own is not an expensive lab test.

Mononucleosis Test Results

The test is designed to give a simple positive or negative result.

Results are typically ready in 5-10 minutes; however, it can sometimes take closer to an hour.

Your doctor may ask you to wait in the exam or waiting room.

What the results mean

A positive monospot result means there are specific antibodies, called heterophile antibodies, present in the blood and you have mono.

A negative result means there are no heterophile antibodies present, and you may not have mono.

If your doctor still suspects mono, they may order the EBV test to confirm.

A positive EBV result confirms that you have EBV antibodies in your blood and shows if you currently have an infection or if were infected in the past.

If the EBV results are negative, it means your symptoms are being caused by something else.

If you do have mono, there is no cure but there are steps you can take to relieve symptoms:

• Stay hydrated
• Get plenty of rest
• Suck on lozenges to soothe your sore throat
• Take over-the-counter medications to relieve pain and fever (e.g. Tylenol)

Mono usually goes away on its own after a few weeks, although the fatigue may last a few months.

Accuracy

Several factors may cause a false negative, including:

• Age: The test is not recommended for kids under four years old because the chance of a false negative is very high.
• Timing of the sample: If the sample is taken too early in the sickness, it can give you a false negative. Make sure to test after being sick for two weeks.
• Mono infection caused by another virus: Mono can be caused by viruses other than the Epstein Barr virus. If you are sick because of a different virus, you will get a false negative.

 If you get a negative monospot test result but you continue to be sick with the symptoms of infectious mononucleosis, your doctor may want to do another test along with the EBV blood test. 

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