Monospot test; Heterophile antibody test
This blood test detects the presence of heterophile antibodies. Heterophile antibodies are antibodies that non-specifically react against different proteins and are useful in the diagnosis of infectious mononucleosis.
How the test is performed
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood).
A needle is inserted into the vein, and the blood is collected in an airtight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
Infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
How to prepare for the test
No special preparation is necessary.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:
- Infant test or procedure preparation (birth to 1 year)
- Toddler test or procedure preparation (1 to 3 years)
- Preschooler test or procedure preparation (3 to 6 years)
- Schoolage test or procedure preparation (6 to 12 years)
- Adolescent test or procedure preparation (12 to 18 years)
How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. You may feel throbbing at the venipuncture site for a few minutes after the blood draw.
Why the test is performed
The mononucleosis test is done to screen for the presence of infectious mononucleosis, a disease caused by the Epstein-Barr virus (EBV). About 1 week after the onset of the disease, many patients develop heterophile antibodies. The antibodies peak at weeks 2 to 5 and may persist for several months to 1 year. A small proportion of patients with mononucleosis may never develop heterophile antibodies.
Normal results are negative, which is indicated by a titer ratio of less than 1:40.
What abnormal results mean
A positive test (titer greater than 1:40) usually indicates infectious mononucleosis. On rare occasions, false-positive tests may be seen with the following:
- Cytomegalovirus infection (CMV)
- Leukemia or lymphoma
- Systemic lupus erythematosus (SLE)
What the risks are
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
- Multiple punctures to locate veins
Monospot tests are usually positive in approximately 85% of patients with infectious mononucleosis. Positive test results will not occur until 1 to 2 weeks into the illness.
by Sharon M. Smith, M.D.
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.