Mono Screen Test

The Mono screen is a quick and commonly used blood test to help diagnose infectious mononucleosis, often called “mono,” which is most frequently caused by the Epstein-Barr virus (EBV). Infectious mononucleosis is sometimes known as the “kissing disease” because it can be spread through saliva. Typical symptoms include extreme fatigue, sore throat, fever, and swollen lymph nodes.

The biology behind the test is based on the detection of heterophile antibodies. These are unusual types of antibodies (proteins made by your immune system to fight infections) that appear when someone is infected with EBV. Although heterophile antibodies are not specific only to EBV, they are highly associated with it.

Accuracy is generally high. sensitivity (the ability to correctly detect mono when it is present) ranges from about 81% to 96%, and specificity (the ability to correctly identify when mono is not present) usually exceeds 90%.

Still, false negatives (when the test misses an infection) can happen, especially early in the course of the disease or in young children. That means a negative test does not completely rule out EBV infection. In such cases, additional testing for EBV-specific antibodies may be needed.

Rarely, false positives can occur if a person has other heterophile antibodies unrelated to EBV infection, such as those seen with certain other infections or immune conditions. Some types of tests can also remain positive for months to over a year after the original infection, though most results return to normal within 2-3 months.