Mononucleosis, a.k.a., the kissing disease, is more prevalent in children and teenagers. But kissing isn't the only cause of this infection, and its flu-like symptoms may delay a diagnosis. There is no cure for mononucleosis, and self-treatment is usually the only way to manage most cases. A trip to the doctor can confirm that your child does indeed have mono, and not some other infection. Here's what will happen when you get there.

Physical Exam to Diagnose Mononucleosis

Your doctor will ask about symptoms such as nausea, headache, sore throat, chills, achy muscles and loss of appetite as well as any knowledge you may have about your child's exposure to someone who has been diagnosed with mononucleosis. A physical exam may reveal white spots in your child's mouth or throat, enlarged lymph nodes, and fever.

Since these signs and symptoms are also common to flu and other illnesses, the doctor may also refer your child for a blood test. When your child's signs, symptoms and test results all indicate mononucleosis, the doctor can make a definite diagnosis.

Blood Tests to Diagnose Mononucleosis

A test known as a complete blood count (CBC) includes a white blood cell count, which is key to diagnosing mononucleosis. A child with mono will have a high white blood cell count because the body starts to produce more white blood cells whenever there is an infection. (White blood cells attack germs and infections and also produce antibodies, which are "fighter" proteins that recognize harmful substances and travel through your bloodstream in an attempt to destroy them.)

Different types of antibodies are produced for different types of infections. When testing for mononucleosis, laboratory technicians use a test called the mono spot to look for specific antibodies that indicate the presence of Epstein-Barr virus, which is usually the cause of mono.

Because an antibody test for mono is not accurate until enough antibodies have been produced, and it takes at least two weeks for antibodies to reach peak levels, accurate blood tests are not possible until the patient has been sick for at least a week or two. That is why an early blood test may be negative, even if your child has some or all of the physical symptoms of mono.

A positive test result means that infectious mononucleosis is present. A false positive result is possible, but normally only in patients who have other medical conditions, such as hepatitis, leukemia, lymphoma, rubella or systemic lupus, where white blood cell count is consistently high. In rare cases, it is also possible to get a false negative result from a mono spot blood test, because some people with mononucleosis never develop the antibodies that help confirm a diagnosis.

If your child's symptoms do not improve over the course of several weeks, or if the mono spot test is negative but the symptoms strongly indicate mono, further blood testing may be necessary to determine the cause of infection.

David Levine, MD, FAAP, reviewed this article.




Bell, AT and Fortune, B. "What Test is the Best for Diagnosing Infectious Mononucleosis?" The Journal of Family Practice Sept 2006;55(9):799-802

Lab Tests Online: Mono Test

University of Maryland Medical Center: Mononucleosis Spot Test