The Test Sample
What is being tested?
RSV testing detects the presence of respiratory syncytial virus (RSV) in nasal secretions. RSV is a common viral respiratory infection that tends to be seasonal, causing community epidemics in young children, older adults, and in the immunocompromised. Outbreaks typically begin in November or December and disappear in early spring. In these high-risk groups, RSV can cause pneumonia and bronchiolitis.
According to the Centers for Disease Control and Prevention (CDC), RSV is the most common cause of pneumonia and bronchiolitis in the U.S. in children under 1 year of age. Almost all children have been infected with the virus by the time they are 2 years old, but less than 2% of these infections are severe enough to require hospitalization. This small percentage still translates to about 75,000 to 125,000 hospitalized children each year, most of them under 6 months old. Their symptoms may include severe coughing, difficulty breathing, and high fevers.
RSV can also be an important cause of respiratory illness in the elderly and in those who are immunocompromised. The World Health Organization (WHO) estimates that globally there may be as many as 64 million cases of RSV infection each year and as many as 160,000 RSV-related deaths.
RSV testing detects virus that is being shed in the respiratory/nasal secretions of an infected person. Since detectable amounts of virus are usually only shed for the first few days of an infection, most testing must be done during this time period. There are several methods to test for the virus, but rapid RSV antigen testing is by far the most popular. Rapid RSV antigen tests are frequently performed on-site, in the doctor's office or the emergency room, with most results available within an hour. In some cases, the sample may be collected and sent to a laboratory for a more sensitive testing method. Results of these RSV tests are usually available the same day.
Occasionally, a doctor will order a viral culture (to grow the RSV virus) or a test to detect the virus's genetic material. These tests have the advantage of identifying not only the RSV virus but also other respiratory viruses that may be present. The main disadvantages of these tests are that they are not available in every laboratory and that the results take longer than the rapid RSV test. This makes them less clinically useful for evaluating an individual, but they can be useful for documenting that RSV or another virus, such as influenza, has reached a community and for identifying outbreaks in particular populations, such as a nursing home, school, or neighborhood.
How is the sample collected for testing?
Sample collection technique is critical in RSV testing. The best and most frequently used sample is a nasal aspirate or wash. A syringe is used to push a small amount of sterile saline into the nose, then gentle suction is applied (for the aspirate) or the resulting fluid is collected into a cup (for a wash).
Sometimes, a nasopharyngeal (NP) swab is used, although it is not preferred because of decreased virus quantity in the sample. The NP swab is collected by having a person tip their head back, then a Dacron swab (like a long Q-tip) is gently inserted into one of the nostrils until resistance is met (about 1 to 2 inches in), then rotated several times and withdrawn. This is not painful, but it may tickle a bit and cause the person's eyes to tear.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.