The respiratory syncytial virus antibody test is a blood test used to diagnose a respiratory syncytial virus (RSV) infection. The test detects the presence of antibodies. Antibodies are proteins that your body’s immune system releases naturally in response to a harmful substance, called an antigen. Specifically, the RSV test detects the presence of antibodies that your body has produced to fight the RSV antigen. The test can be used to diagnose either a recent or a past RSV infection.
According to the Mayo Clinic, RSV is a major cause of human respiratory infections (Mayo). The infection is most severe and occurs most frequently in young children. In infants, the virus can cause bronchiolitis (inflammation of the airways of the lungs), pneumonia (inflammation of the lungs) or croup (swelling of the throat that leads to breathing difficulties and a cough). In older children, adolescents, and adults, infection with RSV tends to be less severe.
The infection is seasonal—from late fall to spring—and commonly occurs as an epidemic. This means that it affects a large number of individuals within a community at the same time. The Centers for Disease Control and Prevention report that nearly all children will be infected with RSV by the time they turn 2 years old, but only a small percentage will experience severe symptoms (CDC).
According to the National Institutes of Health, the RSV antibody test is not very useful. It is not recommended for infants because it may detect the mother’s antibodies, and is not useful in adults because most adults already have antibodies due to past RSV infection (NIH).
Symptoms of an RSV infection are similar to those of other types of respiratory infections and may include:
- a cough
- a runny nose
- a fever
- a decrease in appetite
The test is often performed on premature infants or children under 2 years of age with congenital heart or chronic lung disease or a weakened immune system. According to the CDC, infants and children with these conditions are at highest risk for severe infections, including pneumonia and bronchiolitis, when infected with RSV (CDC).
The RSV antibody test is a blood test performed by a nurse at your doctor’s office. Blood will be drawn from a vein, usually at the inside of your elbow. A blood draw typically involves the following steps:
- The puncture site is cleaned with an antiseptic
- A healthcare provider wraps an elastic band around your upper arm in order to make the vein swell with blood.
- A needle is gently inserted into the vein to collect blood in an attached vial or tube.
- The elastic band is removed from your arm.
- The blood sample is sent to a laboratory for analysis.
No special preparation is required for this test.
Be sure to tell your doctor about any medication (prescription or otherwise) you currently take, because they may affect the results of this test.
As with any blood test, there is a slight risk of bleeding, bruising, or infection at the puncture site. You may feel moderate pain or a sharp prick when the needle is inserted. You may also feel dizzy or lightheaded after the blood draw.
A normal, or negative, test result indicates that there are no antibodies to RSV present in your blood. This means that you have never been infected with RSV.
In infants, a positive test result may indicate that an RSV infection has occurred or that RSV antibodies have been passed from the mother to the baby in utero. In adults, a positive result means that an RSV infection has occurred recently or in the past.
Your doctor can use the results of the test to distinguish between a recent and a past infection. In general, the presence of IgM antibodies indicates recent infection and the presence of IgG antibodies indicates past infection. Most adults and older children have already had an RSV infection and, hence, already have RSV antibodies.
In infants with symptoms of an RSV infection and positive test results, hospitalization is typically not required because symptoms resolve at home in one to two weeks. The CDC states that most children who need to be hospitalized for RSV infection are younger than 6 months of age (CDC). There is no specific treatment available for RSV infection and, at present, no RSV vaccine has been developed.